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UCSB  LIBRARY 


PRACTICAL  TREATISE 


OS  THE 


Combustion  of  Coal. 


ixci.vdinc. 


DESCRIPTIONS    OF    VARIOUS    MECHANICAL    DEVICES    FOR    THE 

ECONOMIC    GENERATION    OF    HEAT    BY    THE 

COMBUSTION    OF    FUEL, 


WHKTHKK 


SOLID,  LIQUID  OR  GASEOUS. 

BY 

WILLIAM  M.  BARR. 


INDIANAPOLIS,   INK 
YOB  X    BROT  II  E  lis. 

187!'. 


COPYRIGHT. 

WILLIAM  M.  BARR, 

1879. 


INDIANAPOLIS: 

BAKER  &  RANDOLPH, 

PRINTERS. 


PREFACE. 


This  hook  is  intended  to  present,  within  a  moderate  compass, 
the  theory  of  the  combustion  of  coal,  with  a  view  to  adapting  it  to 
the  needs  of  that  large  body  of  men  to  whom  this  subject  is  one  of 
great  interest,  but  who.  on  account  of  the  abstruse  style  in  which 
such  books  are  generally  written,  can  not  easily  obtain  the  desired 
information  in  regard  to  the  chemistry  of  coal,  its  combustion,  its 
calorific  power,  and  other  matters  in  this  connection,  which  are  not 
only  of  interest,  but  of  importance  to  themselves. 

Perhaps  no  more  lucid  or  accurate  presentation  of  this  subject 
lias  been  written  for  engineers,  than  that  embodied  in  Professor 
Rankine's  "Steam  Engine  and  Other  Prime  Movers,"  but  that 
work,  excellent  as  it  is  in  itself,  is  to  most  persons  a  book  by  no 
means  easy  to  read,  or  easy  to  use.  It  is  not  that  this  -aibjeet  needs 
to  be  expl  lined  anew,  or  that  there  is  anything  to  add  to  what  has 
already  been  written,  hut  it  is  rather  to  present  to  the  non  mathe- 
matical  reader  that  which  is  accepted  as  high  authority  among 
engineers,  in  a  language  less  difficult  to  understand. 

Tli-  absence  then,  of  any  purely  practical  treatise  of  recent 
date  on  this  subject,  and  the  belief  that  such  a  treatise  would  sup- 
ply a  want  has  induced  the  preparation  of  this  volume.  The 
reader  will  judge  for  himself  how  far  this  want,  if  it  ever  existed, 
ha-  been  met. 

This  book  contains  nothing  that  can  he  said  to  he  new.  hut  its 
usefulness  need  not  be  impaired  on  that  account  if  it  has  the  merit 
of  presenting  this  subject  in  an  accurate  and  intelligible  manner. 
Much  care  bas  been  bestowed  upon  the  work  to  insure  its  accu- 
racy. The  numerous  instances  in  which  the  writer  lias  converted 
French  calories  into  British  units  of  heat,  in  order  to  make  quotations 
in  the  text  of  any  practical   value  to  the  reader,  has  added  not  a 

little  to  tin-  Labor  of  preparation.     Wherever  quotations  have  I n 

made  from  French,  German  or  English  writer-  using  the  metrical 
system,  the  measurements,  quantities  and  temperature  have  been 
re-calculated  and  reduced  to  American  equivalents  ami  Fahren- 
heit degrees. 


IV  PREFACE. 


In  regard  to  authorities,  Professor  Rankin  e's  treatise,  already 
referred  to,  has  been  consulted  at  almost  every  step  wherever 
practicable  and  largely  quoted  from.  Dr.  Percy's  treatise  on 
"Fuel,"  has  also  been  freely  used  and  quoted  from;  so  also,  Watts' 
Dictionary  of  Chemistry;  Ure's  Dictionary  of  Arts,  Manufacturers  and 
Mines;  The  Geology  of  Pennsylvania,  H.  D.  Rogers;  the  Geological 
Reports  of  the  States  of  Ohio,  Indiana  and  Illinois. 

Selections  have  also  been  made  from  well  known  and  reliable 
contributors  to  the  leading  scientific  journals,  including  the 
Engineer,  Engineering,  Scientific  American,  and  others.  The  writer  is 
also  under  many  personal  obligations,  and  especially  so  to  Professor 
E.  T.  Cox,  State  Geologist,  Indiana,  not  only  for  valuable  contribu- 
tions of  matter,  which,  from  his  thorough  knowledge  of  coals,  adds 
much  to  the  value  of  the  book,  but  for  his  personal  interest  and 
assistance  in  the  preparation  of  the  articles  on  the  chemistry  of 
coal. 

Perhaps  an  apology  is  needed  for  the  space  occupied  by  the 
re-print  of  the  report  of  Dr.  Gideon  E.  Moore  on  water-gas.  To 
this  I  can  only  say,  that  it  was  furnished  me  at  my  own  request,  and 
inserted  here  on  the  conviction  that  a  fuel-gas  of  some  sort  is  one  of 
the  pressing  needs  of  the  day ;  and  as  this  report  contains  so  much 
real  information  in  regard  to  water-gas  not  only,  but  to  gaseous 
fuel  in  general,  I  am  sure  it  will  amply  repay  a  careful  read- 
ing, for  I  believe  our  present  imperfect  methods  of  using  crude 
fuels  must,  in  the  larger  cities  at  least,  give  place  sooner  or  later  to 
the  more  economical  employment  of  a  fuel-gas.  The  exceeding 
low  cost  at  which  water-gas  may  be  generated,  its  permanance,  cer- 
tainty, ease  of  management,  cleanliness  and  economy,  are  all,  cer- 
tainly, in  its  favor. 

It  will  be  observed  there  are  repetitions  here  and  there  through 
the  book ;  these  serve  mainly  as  illustrations  in  the  papers  or  lee-' 
tures  quoted  from,  so  that  it  did  not  seem  desirable  to  break  the 
connection  and  re-write  the  sections  containing  them. 

Among  the  works  consulted  and  quoted  from,  are  the  following, 
arranged  in  alphabetical  order,  and  numbered.  Wherever  numbers, 
enclosed  in  brackets,  occur  throughout  the  text,  they  refer  to  the 
publications  corresponding  to  the  numbers  as  given  below. 

Indianapolis,  Ind.,  March  1879, 


A.UTHORS    AND    BOOKS    CONSULTED    OR    Qt'OTED    FROM. 


1.  BKAMWELL,  F.J.     Science  Lectures  at  South  Kensington.     Vol.1.     London,  1S78. 

Macmillan  &  Co. 
■>.  CLARE,  L>.  K.    Manual  of  Hales,  Tables  and  Data,  etc.     London,  1877.     Blakh-  & 

Sou. 
.:.  COOK,  JOSIAH  P.     The  New  Chemistry.     New  York,  1874.     D.  Appleton  &  Co. 

4.  COX,  E.  1.    State  Geologist,  Indiana.    Several  volumes  of  reports  quoted  from,  but 

the  writer  is  also  indebted  for  information  contributed  to  this  work  by  him 
from  his  laboratory  record. 

5.  I  BOOKS  A  ROHERIG.      Metallurgy,  Vol.   3—  Fuel      London,   1*7".      Longmans, 

Green  &  Co. 

6.  DAWSON,  J.  W.      The  Story  of  Earth  and  Iran.     New  York,  1874.     Harper  & 

Bros. 
.;'._..  DWIGHT,  GEORGE  S.,  in  Scientific  American,  Fob.  21.  1877. 

7.  EN-CYCLOPEDIA  BRITANNICA.     IX  Edition. 

i.  ENGINEER.    London.    Several  volumes  quoted  from. 

9.  ENGINEERING.    London.    Several  volumes  quoted  from. 

10.  FARADAY,  MICHAEL.     Chemical  History  of  a  Candle.    New  York,  1861.     Har- 

per A:  Brothers. 

11.  FORNEY,  M.  N.     Catechism  of  the  Locomotive.     New  York,  1875.    The  Railroad 

•  razette. 

12.  FOWNES,  GEORGE.    Elem  nistrg  (Bridges).    Philadelphia,  1871.    Henry 

C.  Lea. 

13.  GRAHAM,  THOMAS  lemislry  (Watts).    New  York,  1857.    Charles 

E.  Bailliere. 
ii.  MAXWELL,  J.  CLERK.     Theory  of  Ileal.    New  York,  1872.     D.  Appleton  &  Co. 
LS    MAXWELL,  J.  CLERK.     L  ctureon  Molecules.     Bradford,  September,  1878. 

16.  McCULLOCH,  U.S.     Mechanical  Theory  of  Beat.     New   fork,  1876.    D.  Van  Nos- 

1 1  and. 

17.  MILLER,  WILLIAM  ALLEN.     Elements  of  Chemistry.    Part  I,  Chemical  Physics. 

\.  w  York,  1872.    John  Wiley  &  Son. 
is.  McFARLANE,  JAMES,  in  th<   Coal  Trade  Journal. 
19  NORTHCOTT,  H.     Steam  Engine.     London,  1877.    Macmillan  &  Co. 
20.  PERCY,  JOHN.    Metallurgy  {Fuel).     London,  1875.    John  Murray. 
•ji.  PRESTON,  3.  TOLVER,  In  the  Engineering  (London). 
22.  KANK1NK.  W.J.  M      Steam  Engine  and  other  Prime  Movert  (Bamher).     London, 

187G.     Charles  Griffin  i   ' 
28.  Rogers,   ll.  It.     Geology  of  Pennsylvania.     Philadelphia,  1858.    J.  B.  Lippin- 

cott  4  Co. 


VI  AUTHORS    AND    BOOKS    CONSULTED. 


24.  SCIENTIFIC  AMERICAN,  New  York.     Several  volumes  quoted  from. 

25.  SCIENTIFIC  AMERICAN.  Supplement,  New  York.     Several  numbers  quoted 

from. 

26.  STEWART,   BALFOUR.       The   Conservation   of   Energy.     New   York,  1874.      D. 

Apple  ton  &  Co. 

27.  STEWART,  BALFOUR.     Elementary  Physics.     London,  1873.     Macmillan  &  Co. 

28.  TAIT,  P.  <i.     Recent  Advances    in  Physical  Science.      London,    1876.     Macmillan 

A   Co. 

29.  TROWBRIDGE,  WILLIAM    P.     Heat  and  Heat  Engines.     New  York,  1874.     John 

Wiley  &  Son. 

30.  TYND ALL,  JOHN.     Heat  as  •<   Mode  of   Motion.     New  York,  1874.      D.  Appleton 

A   Co. 

31.  TYNDALL,  JOHN.     Fragments  of  s<  ;>■„,;■.     New  York,  1*74.      D.  Appleton  a  I  o. 

32.  URE'S  Dictionary  of  Arts,  Mines  and  Manufactures. 

:;:;.   VOGEL,   HERMANN.      Chemistry  of   Light  and  Photography.     New   York.      l>. 

Appleton  A  Co.  ' 

34.   WATTS'  Dictionary  of  Chemistry. 
:;:..  WILLIAMS,  C.  WYE.     Combustionof  Coal  (Weale's  series). 


ERRATA. 


PA<;K.      LINE.  CORRECTIONS  (IN  italics). 

1fi        third  from  top — but  it  also  serves  to  show,  etc. 

25        tenth  from  bottom — but,  taken   i>i  connection  with  furnace  combustion  this  pres- 
sure is  of  importance  as  a  mechanical  agency,  etc. 


CONTENTS. 


CHAPTER  I— Preliminary.  page 
Physical  Properties  of  Coal — Chemical  Properties  of  Bodiei — Divisibility  of 
Matter— Molecules — Atoms — Atomic  and  Molecular  Weights — Equivalent  N  um- 
bers— Symbolic  Notation — Energy — Types  of  Energy — Conversion  of  Visible 
into  Molecular  Energy — Energy  of  Fuel — The  Sun  the  Source  of  Energy — The 
Plants  of  tiie  Coal  Period — The  Atmosphere  of  the  Coal  Period — The  Influence 
of  Light  in  the  Formation  of  Coal — Dissipation  of  Energy 1 

CHAPTER  II— The  Atmosphere. 

Air  the  Source  of  Oxygon  for  Combustion — Composition  of  the  Air — Nitrogen 
— The  Chemical  Compounds  of  Oxygen  and  Nitrogen— Properties  of  Oxj    i 
The  Physical  Properties  of  the  Atmosphere — Absorption  of  Moisture — Cause  of 
Kain — Radiation  of  Heat  through  the  Air — Carbonic  Acid  ami  Ammonia  in  the 
Air — Ozone 25 

CHAPTER  III— Fuels. 

Classification  of  Fuel — Wood — Water  Present  in  Wood — Composition  of  Wood 

— Wood  Charcoal — Combustibility  of  W 1  Charcoal — Peat— Analysis  of   Peat 

— Products  of  the  Distillation  of  Peat — Peatasa  Fuel — Peat  Charcoal — Lignite 
— Difference  between  Lignite  and  Brown  Coal — Lignite  asa  Fuel — Water  in  Lig- 
nite—  Analysis  of  Lignites— Classification  of  Coal — Bituminous  Coal — Analysis 
of  Bituminous  Coals — Non-caking  Coals — Block  Coal — Caking  Coals — Gas  <  loal— 
Coke  -  "I  he  Influence  of  Temperature  and  Pressure  in  the  j  Leld  of  Coke — Cannel 
Coal— Semi-bituminous  ( loaJ  —Semi-anthracite  Coal — Anthracite  Coal :!5 

CHAPTER  IV— Analysis  ok  COAL. 

Analysis,  Chemical,  Qualitative,  Quantitative,  ProximaP — Selection  of  Samples 
for  Analysis — Method  of  Conducting  a  Proximate  Analysis— Elementary  Anal- 
ysis—Determination of  Sulphur  and  Phosphorus — Carbon— Hydrogen — Carbur- 
eted Hydrogen — Sulphur— Products  obtained  Erom  Coal 81 

CHAPTER  V— Combustion. 

Chemical  A  tt  raction— Muriate  of  Zinc— G  unpowdeT — Physical  Changes — Chem- 
ical   Changi  —  Definite   Proportions — Multiple    Proportions — Carbonic    Acid — 
lie  Oxide — Law  of  Equivalents — Energy  of  Chemical  Separation — Nature 

of  Combustion— Conditions  Necessary  to  Combustion     I. Lnosity— Ignition — 

Flame— Recent  Studies  of  Luminous  Flames     Rate  of  C bustion— Tempera- 

tureof  Fin — Weight  and  Specific  Heatof  the  Products  of  Combustion  -Avail- 
able Heat  of  Combustion— Efficiency  Of  a  1'urnace 98 

I'll  a  rii.  i ;  v  i    aii:  Required  fob  Furnace  Combi  stion. 

tions  in  whicb  Oxygen  unites  with  Carbon  and  Hydrogen— Air  required 

led  Air  for  Combustion— Temperature  of  Airsupplied 

to  Blast  Furnaces    The  Hoffman  Kiln— Berthier's  Theory  in  regard  to  Heated 

:  i Observations     Prideaux'  Estimation  of  the  val f  Heated  Air — 

Difficulties  in  Heating  or ling  \  ir  -Proportions  of  Fire-Brick  to  Fuel  burned 

in  the  Siemens  Regenerative  Furnace     Ponsard  Furnace 126 

<  Haiti. i:  \[i    The  Furnace, 

Furnace  Draft — Sectional  Areaof  Chimneys  Height  of  Chimneys  Volume  of 
I  aperature  of  Escaping  Gases — 
Distribution  of  Air  in  th  Admission  of  Air  over  the  Fire  C.  Wye. 
William-'  Plan— T.  s.  Prideaux'  Plan  W.  \  Martin's  Plan  Experimental 
i  the  Martin-Ashcroft  Furna  S.  Navv  Yard,  Washington— 
Admission  of  Air  al  the  Bridge-Wall  (:.  K.  McMurray's  Plan 
for admittj  I   Air  and  Evaporation " 136 

I'll  \  PTEB  \  in     Prodi  i  rs  op  Combi  si  ton. 

Carbonic    L  i    Oxide     Water    Nitrogen    Sulphurous  Oxide    Sur- 

\ir    Smoke     Products  of    Perfect   Combustion    Invisible     How   Soot    is 

d      -inokc-pieveniatives- The   CoiT08ive    Allien  of  Sulphur  On  Bolll 


Vlll  CONTENTS. 


PAGE. 

Ashes  and  Clinker — Analysis  of  Coal  Ashes — Color  of  Ashes  as  Indicating  the 
Presence  of  Iron  Pyrites  in  Coal — The  Formation  of  Clinkers — The  Influence  of 
Iron  in  the  Coal  on  the  Formation  of  Clinker — Apparatus  for  Gas  Analysis 158 

CHAPTER  IX— Thermal  Power  of  Fuels. 

Seat  Developed  hy  Chemical  Action — Favreand  Silberman's  Apparatus — Units 
of  Heat  Evolved  by  Elemental  Combustion — Heat  Developed  by  the  Combus- 
tion of  Coal — Allotropie  States  of  Carbon — Proximate  Constitution  of  Coal — 
Experiments  of  Scheurer-Kestner  and  Meunier-Dollfus  on  the  Calorific  Power 
of  Coal — Thompson's  Calorimeter — Manner  of  Conducting  Experiments — Evap- 
orative Power  of  Coal — Object  in  Reducing  Evaporation  to,  from  and  at  212° 
Kahr 178 

(  II  APTERX— Heat. 

Theory  of  Heat — Mechanical  Force — Chemical  Action — Relation  of  Atomic 
Weights  to  Specific  Heat — Specific  Heat  of  Simple  Gases- -Specific  Heat  and 
Atomic  Weight  of  Elementary  Substances — Specific  Heat — Specific  Heat  of 
Water  in  its  Three  States — Specific  Heat  of  Fuels — Specific  Heat  of  Gases — 
Latent  Heat — Latent  Het  of  Fusion— Latent  Heat  of  Evaporation — Mechanical 
Theory  of  Heat — Joule's  Equivalent — Apparatus  Employed  by  Joule — Unit  of 
Heat 195 

CHAPTER  XI— The  Construction  of  Furnaces. 

Construction  Depends  on  the  Fuel— Conditions  attached  to  a  Good  Furnace — 
Why  Ordinary  Furnaces  are  so  Wasteful — Volatilization  of  Gases  in  the  Fur- 
nan' — Quantity  of  Air  Required — Force  Blast — Description  of  a  Reverberatory 
Furnace — (ts  Advantages — Increase  of  Efficiency  by  the  Use  of  Hot  Air — Loss 
by  Chimney  Draft .'....." :....  208 

CHAPTER  XII— Mechanical  Firing. 

Objections  to  Hand  Firing — Continuous  Firing — The  Requirements  of  a  Self- 
feeding  Mechanism — Description  of  M.  Holroyd  Smith's  Furnace-Feeder 218 

CHAPTER  XIII— Spontaneous  Combustion  of  Coal. 

Must  Likely  to  Occur  on  Board  Ships — Vessels  Lost  from  this  Cause  in  1874— 
Spontaneous  Combustion  begins  in  the  Center  of  the  Heap  or  Middie  of  the 
Cargo — Iron  Pyrites  in  Coal — How  Carbon  Spontaneously  Ignites — Coal  requires 
no  Initial  Temperature  for  its  Combustion — No  Limit  to  the  Heat  which  may 
be  produced  by  Concentration 223 

CHAPTER  XIV— Coal-Dust  Fuel. 

Continuous  Firing — How  a  Furnace  should  be  Fed  when  Using  Powdered  Fuel 
— Experiments  of  United  States  Government  in  187(5 — Comparative  Economy  of 
Powdered  Fuel  as  Compared  with  Ordinary  Coal — Stevenson's  Apparatus  tor 
Burning  Coal-Dust .' 233 

CHAPTER  XV— Liquid  Fuel. 

Analysis  of  Crude  Petroleum — Quantity  of  Air  Required  to  Burn  Oil — Units  of 
Heat" Evolved  by  the  Combustion  of  Oil — Evaporative  Power  of  Crude  00 — 
What  is  Claimed  for  Petroleum  as  a  Fuel — Wise,  Field  and  Aydon's  System  of 
Burning  Liquid  Fuel — Extraordinary  Results  Obtained — Advantages  Arising 
from  its  Use  on  board  Steamships  and  Vessels  of  War 245 

CHAPTER  XVI— Gaseous  Fuel. 

Loss  Attending  the  Use  of  Solid  Fuels — Advantages  Connected  with  the  Use  of 
a  Gas-Fuel — Coal-Gas  for  Domestic  Use — Water-Gas — Volume  of  Water-Gas 
Obtained  for  One  Ton  of  Coal  Burned — Strong's  Process  for  Generating  Fuel- 
Gas — Professor  Gruner  Quoted  on  the  Great  Waste  of  Heat  in  Several  Metallur- 
gical Processes — Comparison  between  the  Efficiency  of  Crude  Coal  and  Water- 
Gas — Calorific  Intensity  of  Water-Gas — Analysis  of  Water-Gas  —  Calorific 
Equivalent  of  Water-Gas — Flame  Temperature — Economic  Value  of  Water- 
Gas— Influence  of  the  Specific  Heat  of  the  Products  of  Combustion  of  Water- 
Gas — Water-Gas  as  an  Illuminating  Agent — Objections  to  Water-Gas 254 

CHAPTER  XVII — Utilizing  Waste  Gases  from  the  Furnace. 

Waste  Products — Magnitude  of  the  loss — Siemens'  Regenerative  Gas  Furnace....  284 

CHAPTER  XVIII— A.  Ponsard's  Process  and  Apparatus  for  Generating 
Gaseous  Fuel 290 


CHAP  TEE   I. 
«. 

PRELIMINARY. 

Physical  Properties  of  Coal — Chemical  Properties  of  Bodies — Divisi- 
bility of  Matter — Molecules — Atoms — Atomic  and  Molecular 
Weights — Equivalent  Numbers — Symbolic  Notation — Energy — 
Types  of  Energy — Conversion  of  Visible  into  Molecular  Energy 
— Energy  of  Fuel — The  Sun  the  Source  of  Energy — The  Plants 
of  the  Coal  Period — The  Atmosphere  of  the  Coal  Period — The 
Influence  of  Light  in  the  Formation  of  Coal — Dissipation  of 
Energy. 

ll<e  Physical  Properties  <>f  Coal  include  most  of  the 
general  properties  of  matter.  It  belongs  to  the  non- 
metallic  class  of  bodies,  is  a  solid,  varying  in  structure 
from  hard  crystalline,  as  in  the  case  of  pure  anthracite. 
through  all  gradations  to  a  compact  earthy  body  bear- 
ing a  close  resemblance  to  wood,  both  in  structure  and 
appearance,  and  presenting  no  distinct  crystalline  frac- 
ture when  broken.  In  color  it  varies  from  black  to 
dark  In-own.  It  i>  always  brittle,  and  may  easily  be 
broken  into  fragments.  Anthracites  do  not  fuse  at  all 
in  the  lire;  bituminous  coals  sometimes  fuse,  but  not 
without  decomposition.  Jn  specific  gravity  it  varies 
from  1..",.-)  to  1.20. 

Coal  occurs  in  strata  of  varying  thickness  and  purity. 
Carbon  and  hydrogen  arc  its  chief  elements,  and  are 
those  which  allow  its  use  with  advantage  as  a  source  of 
heat. 

(2) 


COMBUSTION    OF    COAL. 


7"  Chemical  Properties  of  a  Body  arc  those  which 
relate  to  its  action  upon  other  bodies,  and  to  the  perma- 
nent changes  which  it  experiences  in  itself,  or  which  it 
effects  upon  them.  When  a  body  undergoes  chemical 
change  it  almost  invariably  destroys  the  physical  prop- 
erties held  by  it  previous  to  this  change,  but  experiment 
has  fully  demonstrated  that  matter  is  indestructible,  so 
that  whatever  changes  are  made  in  the  physical  appear- 
ance or  form  of  matter  by  any  chemical  process,  none 
of  it  is  destroyed. 

Divisibility  of  Matter — A  piece  of  coal  maybe  divided 
and  subdivided  until  it  is  reduced  to  an  impalpable  pow- 
der and  still  retain  all  the  characteristics  of  coal,  and 
we  might  keep  on  dividing  a  single  grain  of  this  coal — 
if  our  senses  were  acute  enough  to  detect,  and  we  had 
instruments  sufficiently  delicate  to  perform  the  subdivis- 
ions— until  at  last  there  would  be  a  piece  no  longer  cap- 
able of  being  subdivided  without  destroying  its  com- 
position or  nature,  there  would  then  be,  as  a  final  result, 
a  molecule  of  coal.  If  we  were  to  analyze  this  molecule 
of  coal  we  would  find  it  to  be  composed  of  several  sub- 
stances, such  as  carbon,  hydrogen,  oxygen,  nitrogen, 
etc.,  so  that  taking  a  molecule  of  coal  we  may  reduce  it 
to  the  elementary  substances,  which  gave  it  character. 
These  elementary  substances  are  capable  of  farther 
subdivision  in  the  same  manner,  and  if  any  molecule 
were  separately  subdivided  until  it  was  no  longer  pos- 
sible to  divide  it  again,  such  a  piece  would  be  called  an 
atom — not  of  coal,  but  of  carbon,  hydrogen,  oxygen,  or 
whatever  else  it  might    be.      This   process    would   be 


MOLECULES. 


partly  mechanical  and  partly  chemical.  The  crushing 
or  reducing  to  powder  would  be  mechanical;  the  resolv- 
ing of  the  coal  into  its  elements  by  decomposition  is  a 
chemical  process.  Any  compound  substance  may  be 
resolved  into  its  constituent  molecules,  and  these  into 
atoms,  which  is  the  ultimate  limit  of  the  divisibility  of 
matter. 

Molecules  (15) — An  atom  is  a  body  which  can  not  be 
cut  in  two.  A  molecule  is  the  smallest  possible  portion 
of  a  particular  substance.  Any  substance,  simple  or 
compound,  has  its  own  molecule.  If  this  molecule  be 
divided,  its  parts  are  molecules  of  a  different  substance 
or  substances  from  that  of  which  the  whole  is  a  molec- 
ule. An  atom,  if  there  is  such  a  thing,  must  be  a  molec- 
ule of  an  elementary  substance. 

The  old  atomic  theory,  as  described  by  Lucretius  and 
revived  in  modern  times,  asserts  that  the  molecules  of 
all  bodies  are  in  motion,  even  when  the  body  itself 
appears  to  be  at  rest.  These  motions  of  molecules  are, 
in  the  case  of  solid  bodies,  confined  within  so  narrow 
a  range  that  even  with  our  best  microscopes  we  can  not 
deteet  that  they  alter  their  places  at  all. 

In  liquids  and  gases,  however,  the  molecules  are  not 
confined  within  any  definite  limits,  but  work  their  way 
through  the  whole  mass,  even  when  that  mass  is  not  dis- 
turbed by  any  visible  motion.  This  process  of  diffusion, 
as  it  is  called,  which  gdcs  on  in  gases  and  lifpiids  and 
even  in  some  solids,  can  be  subjected  to  experiment  and 
forms  one  of  the  mosl  convincing  proofs  of  the  motion 
of  molecules.    Now,  the  recent  progress  of  molecular 


COMBUSTION    OF    COAL. 


science  began  with  the  study  of  the  mechanical  effect  of 
the  impact  of  these  moving  molecules  when  they  strike 
against  any  solid  body.  Of  course  these  flying  molec- 
ules must  beat  against  whatever  is  placed  among  them, 
and  the  constant  succession  of  these  strokes  is,  accord- 
ing to  our  theorv,  the  sole  cause  of  what  is  called  the 
pressure  of  air  and  other  gasses. 

'We  all  know  that  air  or  any  other  gas  placed  in  a 
vessel  presses  against  the  sides  of  the  vessel,  and  against 
the  surface  of  any  body  placed  within  it.  On  the  kin- 
etfc  theory  this  pressure  is  entirely  due  to  the  molecules 
striking  against  these  surfaces,  and  therebv  communi- 
eating  to  them  a  series  of  impulses,  which  follow  each 
other  in  such  rapid  succession  that  they  produce  an 
effect  which  can  not  be  distinguished  from  that  of  a 
eontinuous  pressure.  If  the  velocity  of  the  molecules 
is  given,  and  the  number  varied,  then  since  each  molec- 
ule on  an  average  strikes  the  side  of  the  vessel  the 
same  number  of  times,  and  with  an  impulse  of  the  same 
magnitude,  each  will  contribute  an  equal  share  to  the 
whole  pressure. 

The  pressure  in  a  vessel  of  a  given  size  is,  therefore, 
proportional  to  the  number  of  molecules  in  it,  that  is 
to  the  quantity  of  gas  in  it. 

This  is  the  complete  dynamical  explanation  of  the 
fact  discovered  by  Robert  Boyle,  that  the  pressure  of  air 
is  proportioned  to  its  density.  It  shows  also  that  of  dif- 
ferent portions  of  gas  forced  into  a  vessel,  each  produces 
its  own  part  of  the  pressure  independent  of  the  rest,  and 
this  whether  these  portions  be  of  the  same  gas  or  not. 


ATOMIC    AXD    MOLECULAR    WEIGHTS. 


Atomic  and  Molecular  Weights  —  "Equivalent  num- 
bers" are  often  used  to  express  either  atomic  or  molec- 
ular weights,  and  not  unfrequently  both.  Confusion 
arises  in  not  stating  in  precise  terms  which  of  the  two 
is  meant.  By  referring  to  one  book  we  find,  11  — 1,  C 
=  6,  0  =  8  and  S  =  16,  etc.  By  referring  to  another  book 
we  find,  11  =  1,  C  =  12,  0  =  16  and  S  =  32,  etc.  The  law 
of  definite  proportion  assumes  that  atoms  have  definite 
weight;  that  an  atom  is  a  definite  and  fixed  quantity; 
that  atoms  of  the  same  substance  are  of  the  same  size 
and  weight.  The  confusion  arises  not  that  matter  has 
changed,  or  that  the  law  of  proportion  has  changed,  but 
the  nomenclature  of  the  new  chemistry  is  different  from 
the  old  in  the  introduction  of  the  word  molecule  as  a 
substitute  for  the  word  atom  as  it  was  generally  used, 
and  though  still  retaining  it,  gives  it  a  specific  mean- 
ing which  is  not  synonymous  or  equivalent  to  the  word 
molecule. 

This  word  molecule  means  simply  a  small  mas-  of 
matter  or  the  smallest  portion  of  a  particular  substance; 
an  atom  means  indivisible. 

Hydrogen  being  the  lightest  known  substance,  has, 
by  general  consent,  been  made  the  unit  of  comparison. 
Tt  is  to  be  supposed,  to  begin  with,  that  a  molecule  of 
hydrogen  consists  of  two  atom-:  hence,  if  the  atomic 
weight  of  hydrogen  is  to  be  taken  as  1,  the  molecular 
weight  is  2.  (7).  In  order  to  ascertain  the  molocular 
weights  of  other  substances — that  i-  to  say.  the  relative 
weights  of  their  molecules  referred  to  that  of  hydrogen 
— it   is   merely  necessary  to  determine   their   densities 


COMBUSTION    OF    COAL. 


referred  to  hydrogen  as  unity,  and  then  multiply  their 
densities  by  2. 

When,  however,  the  molecular  weights  of  the  ele- 
ments are  compared  with  their  atomic  weights  it  is 
found  they  do  not  always,  as  in  the  case  of  hydrogen, 
double  their  atomic  weights;  hence  it  is  inferred  that 
the  molecules  of  elements  do  not  all  contain  two  atoms. 
In  a  few  cases  the  atomic  weights  and  the  molecular 
weights  agree,  which  necessitates  the  conclusion  that 
the  molecules  are  monatomic  or  consist  of  a  single  atom; 
in  a  few  other  cases  the  molecular  weight  is  either  four 
or  six  times  the  atomic  weight,  and  the  molecules  are 
therefore  regarded  as  tetratomic  or  hexatomic;  that  is, 
containing  four  or  six  atoms. 

The  following  table  gives  the  molecular  weight  of 
the  constituents  of  coal  as  ordinarily  determined  by 
analysis,  adding  phosphorus  which  occurs  occasionally, 
but  more  particularly,  to  exhibit  its  molecular  as  com- 
pared with  the  atomic  weight,  illustrating  what  was  said 
in  the  preceding  paragraph: 

Table  I — Molecular  Weights. 


Hydrogen. .. 

Carbon 

Nitrogen 

Oxygen 

Phosphorus 
Sulphur 


H 

C 
N 
0 
P 

s 


ATOMIC 
WEIGHT. 


1 

12 
14 
16 
31 
29 


MOLECULAR 
WEIGHT. 


2 

24 

28 

32 

124 

64 

192 


NUMBER    OF 

ATOMS   I.V 
A  MOLECULE. 


ATOMIC    AND    MOLECULAR    WEIGHTS. 


It  will  bo  soon  that  two  numbers  arc  given  for  sul- 
phur. This  is  because  at  temperatures  above  800°  C. 
(1472°  Fahr.)  the  density  of  sulphur  vapor  is  such  as  to 
indicate  that  the  sulphur  molecule  consists  of  two  atoms, 
whereas  its  density  at  about  500°  C.  (932°  Fahr.)  is  three 
times  as  great,  and.  consequently,  it  is  said  to  be  sup- 
posed that  the  molecules  are  hexatomic  or  contain  six 
atoms. 

Table  II  contains  a  list  of  elements  found  in  coal  by 
elementary  analysis. 

Table  II. 


Aluminum Al. 

( 'allium Ca. 

<  !arbon C. 

Hydrogen ,  II. 

Iron Fc. 

Magnesium '  Mg 

Nitrogen X. 

< » -^  >  -r<  •  • » O. 

Phosphorus j  P. 

Potassium K. 

Silicon !  Si. 

Sulphur S. 


ATOMIC 
WEIGHT. 


27.5 

4o. 
12 
1 
56 
24 
14 
It. 
31 
3<J 
28 

39 


The  column  <>f  atomic  weights  in  this  tabic  means 
thai  one  atom  of  carbon  is  twelve  times  as  heavy  as 
hydrogen,  oxygen  sixteen  times  as  heavy,  nitrogen  four- 
teen times  as  licav\ .  etc. 


8  COMBUSTION    OF   COAL. 

A  distinction  must  l>e  made  between  atomic  weights 
and  equivalent  numbers.  They  do  not  mean  the  same 
thing.  The  equivalent  or  combining  proportion  is 
an  experimental  constant  which  is  independent  of  the- 
oretical considerations;  (17)  but  the  relative  atomic 
weight  is  necessarily  a  matter  of  inference,  and  may  be, 
a  number,  often  a  multiple  of-  the  equivalent,  and 
selected  by  the  chemist  from  theoretical  considerations, 
based  partly  upon  the  law  of  gaseous  volumes,  partly 
on  chemical  grounds,  partly  on  the  phenomena  of  spe- 
cific heat. 

The  law  of  gaseous  volumes,  as  laid  down  by  Avo- 
gadro,  means  that  equal  volumes  of  all  gasses  under  the 
same  conditions  have  the  same  number  of  molecules  (3). 
Then,  since  a  given  volume  of  oxygen  gas  weighs  six- 
teen times  as  much  as  the  same  volume  of  hydrogen  gas 
the  molecule  of  oxygen  must  weigh  sixteen  times  as 
much  as  the  molecule  of  hydrogen ;  and,  if  we  assumed 
the  hydrogen  molecule  as  the  unit  of  molecular  weight, 
the  molecule  of  oxygen  would  weigh  sixteen  of  these 
units,  hence  the  atomic  weight  of  oxygen  would  be  six- 
teen. 

Symbolic  Notation — In  the  preceding  tables,  the  let- 
ters H  for  hydrogen,  C  for  carbon,  etc.,  appear;  this  is 
for  two  reasons : 

1.  It  belongs  to  an  agreed  symbolic  language  by 
which  elements  may  be  recognized  at  sight  by  the  use 
of  the  first  letter,  as  far  as  practicable,  of  its  Latin 
name. 


SYMBOLIC   NOTATION.  9 


2.  It  facilitates  the  representation  of  chemical 
changes,  by  which  reactions  of  a  complicated  character 
may  be  understood  at  a  glance. 

These  symbols  are  not  simply  abbreviations  of  the 
names  of  the  elements,  but  represent  the  atomic  weights 
of  the  elements  for  which  they  stand;  thus,  C  repre- 
sents carbon  not  only,  but  its  atomic  weight  as  well, 
arid  may  be  expressed  as  follows:  Carbon  =  C  =12. 
This  is  not  an  exact  expression,  but  serves  to  show  the 
value  of  C  as  a  symbol,  representing  the  name  of  the 
element  carbon,  and  its  atomic  weight,  12.  "Whenever 
a  symbol  is  used  singly,  it  means  an  atom  of  the 
element  represented ;  C  represents  carbon  not  only,  but 
one  atom  of  carbon.  A  combination  of  elements  is 
represented  by  a  combination  of  symbols  placed  side  by 
side;  thus — one  atom  of  carbon  and  one  atom  of 
oxygen  would  be  expressed  as  CO,  and  by  this  we 
mean  carbonic  oxide,  a  very  common  product  of  the 
combustion  of  coal. 

We  also  understand  by  this,  that  one  atom  of  carbon 
and  one  atom  of  oxygen  combine  to  form,  not  one  atom, 
but  one  molecule,  of  carbonic  oxide. 

Suppose  we  added  to  the  molecule  of  carbonic  oxide 
(CO),  another  atom  of  oxygen,  or  CO  +  O,  we  under- 
stand  the  compound  to  consist  of  one  atom  of  carbon 
and  two  atoms  of  oxygen,  and,  as  a  less  complicated 
expression  the  formula  CO.,  is  used.  This  is  the  sym- 
bolic expression  of  one  molecule  of  carbonic  acid,  the 
product  of  the  complete  combustion  of  carbon  and 
oxygen.     The  atomic  value  of  each  element  in  a  com- 


10  COMBUSTION   OF    COAL. 

pound  remains  unchanged,  and  the  aggregate  weight  of 
the  atoms  forms  the  molecular  weight  of  the  compound, 
whatever  it  may  he. 

One  molecule  of  carbonic  acid  =  one    atom    carbon    C  X   12  =  12 

two  atoms  of  oxygen  Oi  X  1G— 32 


CO,  =44 
the  weight  of  one  molecule  of  carbonic  acid. 

Whenever  two  or  more  atoms  of  a  body  enter  into 
the  formation  of  a  molecule,  it  is  most  conveniently 
expressed  by  writing  a  small  figure  to  the  right  of  the 
letter  and  below  the  line,  whenever  practicable,  or 
making  it  smaller  than  the  symbol,  when  not  so; 
C3  indicates  three  atoms  of  carbon,  II8  =  8  atoms  of 
hydrogen;  C3  H8  is  the  formula  for  one  of  the  products 
of  coal  occurring  in  the  Marsh  gas  series,  and  known 
as  prophyl  hydride,  and  this  formula  is  the  expression 
of  one  molecule.  2  C3  H8  would  be  the  expression  repre- 
senting two  molecules,  and  so  on. 

Secondary  compounds,  such  as  salts,  are  expressed 
in  an  analogous  way,  the  metal  being  usually  placed 
first,  Ca  CO.,  representing  one  molecule  of  carbonate  of 
calcium — caleium  being  the  metallic  base  (17). 

When  a  comma  is  used  to  separate  two  compounds, 
a  more  intimate  union  is  supposed  than  when  the  sign 
-f  is  used. 

Suppose  in  the  analysis  of  the  product  of  the  com- 
bustion of  coal  we  have  in  100  parts  the  formula  87 
C02  +  18  1I2  0  as  representing  the  constituents  of  the 
sample  analyzed.     It  means  that  87  per  cent,  is  carbonic 


TYPES    OF    ENERGY.  11 


acid,  and  13  per  cent,  water  or  vapor,  as  the  latter  will 
probably  be  condensed  and  disappear,  while  the  former 
may  still  retain  its  permanancy  as  a  gas;  the  sign  —  is 
interposed  to  separate  or  distinguish  the  one  from  the 
other. 

A  very  little  practice  will  enable  one  to  determine 
at  sight  the  elements  in  any  formulated  compound,  and 
give  to  each  its  proper  atomic  weight. 

Energy  is  the  power  of  doing  work.  By  work  is 
meant  overcoming  resistance.  If  a  body  weighing  one 
pound  be  lifted  one  foot  high  against  the  action  of 
gravity,  we  have  then  the  unit  of  work  called  a  foot- 
/>•<<'/<>/.  Thirty-three  thousand  pounds  raised  one  foot 
high  in  a  minute  is  called  a  horse-power.  Five  hun- 
dred and  fifty  pounds  raised  one  foot  high  in  a  second 
amounts  to  the  same  thing,  because:  550  lbs.  X  60 
sec.  —  83,000  lbs.  one  foot  high  in  60  seconds  orl  minute. 

The  unit  of  work  as  laid  down  in  most  foreign  sci- 
entific books  is  the  kilogram  met  re ;  this  represents  the 
work  done  in  raising  one  kilogramme  one  metre  high 
against  the  force  of  gravity  at  the  earth's  surface.  This 
unit  of  work  is  rarely  used  in  this  country,  and.  unless 
otherwise  stated  when  used,  we  shall  employ  the  foot- 
pound as  the  unit  of  work  in  this  book. 

Types  of  Energy — Energy  is  of  two  types,  known  as 
kinetic  and  potential. 

Kinetic  energy  is  the  energy  due  to  motion. 
Potential  energy  i.-  the  energy  due  to  position. 


12  COMBUSTION    OF    COAL. 

Let  us  suppose  a  brick  house  in  course  of  erection, 
and  attained  a  height  of,  say,  twenty  feet  above  the 
ground;  a  man  standing  on  the  ground  may  throw  a 
brick  to  another  man  on  the  scaffold,  at  that  height.  If, 
instead  of  using  his  muscular  strength  to  throw  the 
brick  to  that  height,  he  simply  "  let  go  "  of  the  brick,  it 
would,  in  obedience  to  the  law  of  gravitation,  fall  to  the 
ground;  but,  instead,  he  gives  the  brick  a  toss,  and  it 
ascends  against  the  attraction  of  the  earth  to  something 
more  than  the  height  of  the  scaffold,  ceases  to  rise,  and 
begins  to  fall  when  the  man  above  catches  it,  and  places 
it  beside  him  on  the  scaffold.  We  have  in  this  simple 
illustration  examples  of  the  two  types  of  energy.  The 
flight  of  the  brick  upwards  is  due  to  the  impulse  it 
received  at  the  hands  of  the  man  on  the  ground — it  is  a 
consequence  of  muscular  effort — it  is  an  example  of 
work  done,  because,  resistance  has  been  overcome.  The 
brick  in  its  flight  has  a  property  which  it  did  not  have 
on  the  ground.  That  property  is  energ}- — energy  due 
to  motion,  or  kinetic  energy.  The  amount  of  energy  or 
capacity  it  has  for  doing  work  is  a  certain  quantity,  and 
is  equal  to  the  weight  of  the  brick  multiplied  into  the 
height  it  ascended  above  the  man's  hands  before  it  began 
its  downward  flight. 

The  brick  on  the  scaffold  is  at  a  state  of  rest,  but  it 
has  not  lost  its  energy.  It  is,  however,  of  a  different 
type  from  that  in  the  preceding  paragraph.  The  brick 
on  the  scaffold,  though  at  rest,  has  a  capacity  for  doing- 
work  simply  on  account  of  its  elevation. 


VISIBLE  INTO  MOLECULAR  OR  INVISIBLE  ENERGY.  13 

This  is  called  the  energy  of  position  or  potential 
energy.  Suppose  the  brick  to  be  pushed  over  the  edge 
of  the  scaffold  ;  it  will  fall  by  virtue  of  gravitation,  and 
when  it  reaches  the  height  of  the  man's  hands,  from 
which  the  brick  was  projected  upward,  the  two  energies 
will  exactly  equal  each  other,  except  in  so  far  as  it  is 
modified  by  the  resistance  of  the  air.  This,  however, 
gives  no  exception  to  the  general  truth  of  the  principle 
of  conservation  of  energy,  because  any  energy  lost  by 
the  brick  is  communicated  without  loss  of  quantity  to 
the  surrounding  air. 

These  two  kinds  of  energy,  energy  of  motion  and 
energy  of  position,  are  being  continually  changed  one 
into  the  other.  An  illustration  of  this  conversion  of 
one  form  of  energy  to  another  is  seen  in  a  head  of  water 
employed  to  turn  a  water  wheel.  The  water  in  the  dam 
possesses  energy  on  account  of  its  height  above  the 
wheel.  The  weight  of  this  water  impinging  against  the 
anus  of  the  wheel  imparts  motion  to  it,  and,  we  have 
in  tin'  wheel  a  store  of  energy  due  to  motion,  which,  by 
suitable  connections,  is  capable  of  doing  work.  This  is 
an  example  of  the  transmutation  of  energy;  that  is,  the 
changing  of  one  kind  of  energy  into  another.  There 
are  many  varieties  of  visible  energy,  hut  there  is  energy 
which  is  invisible,  and,  the  one  may  be  converted  into 
the  other.  The  most  common  illustration  of  this  is  the 
conversion  of  work  into  heat. 

Conversion  of  Visible  n<i<>  Molecular  or  Invisible  Energy 

— This  occur.-  when  motion  is  arrested,  whether  by  per- 
ctission  or  by  friction.     It  is  the  conversion  of  work  into 


14  COMBUSTION   OF    COAL. 

heat.  If  a  lead  bullet  be  fired  against  an  iron  target  its 
motion  is  destroyed  by  impact,  but  not  so  its  energy. 
The  ball  will  have  performed  work  in  the  act  of  flatten- 
ing itself,  and  in  rebounding  from  the  target,  but  in 
addition  to  this  it  will  be  found  to  be  quite  hot.  If  we 
had  an  instrument  delicate  enough  to  measure  the  tern- 
perature  of  the  target  after  the  ball  had  come  in  contact 
with  it,  we  would  find  it  to  be  higher  than  it  was  before 
the  ball  struck  it.  If  we  could  gather  together  the 
friction  of  the  ball  in  the  gun,  the  resistance  of  the  ball 
in  the  air,  the  work  done  in  overcoming  gravitation,  the 
work  done  in  the  act  of  flattening  the  ball,  the  work 
done  in  the  rebound,  the  work  done  in  producing  the 
tremor  of  the  target,  together  with  the  heat  generated 
by  impact,  we  would  then  have  an  amount  of  energy 
exactly  equal  to  the  energy  imparted  to  the  ball  by  the 
powder  at  the  moment  of  explosion.  A  conversion  of 
visible  or  actual  energy  into  heat. 

If  two  pieces  of  dry  wood  are  rubbed  together  with 
considerable  pressure  they  get  quite  hot,  and  it  is  possi- 
ble, if  this  rubbing  were  continued  long  enough,  they 
would  in  time  "take  fire"  and  burn.  The  ordinary 
explanation  of  this  is,  that  heat  has  been  generated  by 
friction.  This  is  quite  true,  but  it  is  also  to  be  explained 
on  the  theory  that  work  has  been  converted  into  heat. 

The  great  characteristic  of  energy  is,  that  it  may  be 
transformed  or  transmuted  from  one  kind  of  energy  into 
another  kind  of  energy,  but  through  all  its  transforma- 
tions the  quantity  present  always  remains  the  same; 
though  known  by  different  names,  we  ought  not  to  for- 


ENERGY   OF   FUEL.  15 


get  that  energy  is  always  the  same  thing,  and  the  various 
names  given  to  energy  are  simply  those  of  convenience 
in  classification. 

Energy  of  Fuel — The  principal  fuel  in  all  civilized 
countries  is  coal.  It  contains,  within  an  unattractive 
exterior,  a  store  of  energy  almost  incredible.  Having 
an  area  in  this  country  alone,  of  nearly  two  hundred 
thousand  square  miles  of  coal  formation,  we  may  form 
some  idea  of  this  vast  force  now  latent,  but  ready  to  obey 
the  law  of  its  nature,  demanding  only  that  the  conditions 
be  favorable  for  the  conversion  of  its  constituent  elements, 
through  the  agency  of  a  chemical  union  with  oxygen, 
in  order  to  convert  this  passive  and  inert  mass  of  car- 
bonaceous  matter  into  heat,  a  force,  capable  of  per- 
forming greater  or  less  work  through  the  medium  of 
heat  engines,  as  the  conditions  are  more  or  less  favora- 
ble for  economic  conversion. 

The  greater  part  of  the  coal  formation  in  this  coun- 
try is  bituminous;  it  contains  less  carbon  than  anthra- 
cite, bul  its  heating  power,  pound  for  pound,  is  not 
much  less  if  pure,  and  free  from  earthy  matter.  The 
volatile  portions  being  rich  in  hydro-carbon,  giving  off 
great  heat  it'  combustion  is  perfect. 

The  energy  of  fuel  or  its  power  to  do  work  may 
easily  be  computed  by  assuming  a  value  of  14,500  heat 
units  in  one  pound  of  coal,  this  multiplied  by  772,  the 
thermal  unit  known  as  Joule's  equivalent  would  give: 
14,500  772  =  11,194,000  pounds  raised  one  fool  high  in 
one  minute,  representing  the  potential  energy  of  one 
pound  of  coal. 


16  COMBUSTION    OF    COAL. 


This  of  course  represents  the  utmost  limit  of  work 
in  one  pound  of  coal,  and  which  never  can  be  arrived  at 
in  practice,  but  it  also  seems  to  show  the  vast  store  of 
energy  in  the  coal,  and  the  latent  force  capable  of  min- 
istering to  our  needs,  by  the  simplest  mechanism. 

The  Sun  the  Source  of  Energy — If  we  would  know 
the  beginnings  of  coal  formation  we  must  go  back 
through  the  ages  to  the  period  known  as  the  carbon- 
iferous age.  Coal  is  believed  to  be  vegetable  matter, 
which  has  undergone  both  chemical  and  mechanical 
changes  during  the  ages  in  which  it  has  been  buried 
under  the  strata  of  the  earth's  crust.  The  flora  of  that 
period  was  rank  in  the  extreme;  fortunately,  specimens 
occur  by  which  a  "restoration"  of  the  characteristic 
plants  which  play  so  important  a  part  in  coal  formation 
having  been  carefully  removed,  and  serve  to  show  not- 
only  the  structure  of  the  plant,  interesting  in  itself,  but 
gives  us  an  idea  from  our  knowledge  of  tropical  vegeta- 
tion how  intense  the  heat,  and  how  humid  the  atmos- 
phere, laden  with  carbonic  acid,  stimulating  all  vegeta- 
tion to  collossal  growth. 

Wood  exposed  to  the  oxygen  of  the  atmosphere  is 
slowly  but  entirely  rotted  and  destroyed ;  even  if  buried, 
the  oxygen  having  access  through  the  particles  of  sand 
will  in  time  produce  the  same  result;  but  if  the  action 
of  the  oxygen  of  the  atmosphere  is  nearly  or  entirely 
prevented,  the  woody  matter  is  slowly  burned  into  coal. 
This  proceeding  does  not  come  to  its  end  without  a 
great  many  changes.  One  of  these  modifications  is  the 
transformation  of  the  woodv  matter  into  a  soft  black 


THE    SUN   TIIE    SOURCE    OF    ENERGY.  17 

mud;  the  ever-increasing  strata  above  this  formation 
varying  from  hundreds  to  thousands  of  feet  crushes 
together  the  cell  walls  of  the  vegetable  matter,  pro- 
ducing not  only  a  flattening  but  a  hardening  effect  by 
reason  of  this  immense  pressure,  the  intensity  of  which 
may  be  imagined  if  we  suppose  earth,  rock,  etc.  t® 
weigh  about  eighty  pounds  per  cubic  foot  on  an  average. 

The  most  conspicuous  and  abundant  of  the  trees  of 
the  coal  period  was  the  sigillaria  or  seal  tree.  They  grew 
to  a  height  from  thirty  to  sixty  feet,  though  the}'  are 
said  to  have  attained  a  height  of  seventy  feet  and 
a  diameter  of  live  feet.  They,  more  than  any 
otlnr  genus  of  plants,  contributed  to  the  coal  forma- 
tion. Some  twenty-eight  varieties  of  this  tree  are 
described  in  the  Geology  of  Pennsylvania — Kogers — 
vol.  ii,  p.  871-:. 

"These  trees  (6)  present  tall,  pillar-like  trunks, 
and  marked  by  rows  of  scars  left  by  the  fallen  leaves. 
They  are  sometimes  branchless,  or  divide  at  the  top 
into  a  few  thick  limbs,  covered  with  lone,  rigid 
grass-like  foliage.  On  their  branches  they  bear  long, 
slender  spikes  of  fruit,  and  we  may  conjecture  that 
quantities  of  nut-like  Beeds  scattered  over  the  ground 
around  their  trunks  are  their  produce.  If  we  approach 
one  of  these  trees  closely,  more  especially  a  young  spec- 
imen not  yet  furrowed  by  age,  we  are  amazed  to  observe- 
the  accurate  regularity  and  curious  tonus  of  the  leaf- 
scar-, and  the  regular  ribbing  SO  very  different  from  that  of 
our  ordinary  forest  trees.      If  we  cut  into  its  stem,  we  arc 

still  further  astonished  at  its  singular  structure.      Kxter- 
(3) 


18  COMBUSTION   OF    COAL. 

nally  it  has  a  firm  and  hard  rind;  within  this  is  a  great 
thickness  of  soft  cellular  inner  hark,  traversed  by  large 
bundles  of  tough  fibres.  In  the  center  is  a  core  or  axis 
of  woody  matter,  very  slender  in  proportion  to  the  thick- 
ness of  the  trunk,  and  still  further  reduced  in  strength 
by  a  large  cellular  pith.  Thus  a  great  stem  four  or  live 
feet  in  diameter  is  little  else  than  a  mass  of  cellular  tis- 
sue, altogether  unfit  to  form  a  mast  or  beam,  but  excel- 
lently adapted,  when  flattened  and  carbonized,  to  blaze 
upon  our  winter  hearth  as  a  flake  of  coal.  The  roots  of 
these  trees  wTere  perhaps  more  singular  than  their  stems; 
spreading  widely  in  the  soft  soil  by  regular  bifurcation, 
they  ran  out  in  long,  snake-like  cords,  studded  all  over 
with  thick  c3Tlindrical  rootlets,  which  spread  from  them 
in  every  direction.  They  resembled  in  form,  and  proba- 
bly in  function,  those  cable-like  root-stocks  of  the  pond- 
lilies,  which  run  through  the  slime  of  lakes,  but  the  struct- 
ure of  the  rootlets  was  precisely  that  of  those  of  some 
modern  Cycads.  It  was  long  before  these  singular  roots 
were  known  to  belong  to  a  tree.  They  were  supposed 
to  be  branches  of  some  creeping  aquatic  plant,  and  bot- 
anists objected  to  the  idea  of  their  being  roots;  but  at 
length  their  connection  with  sigillaria  was  observed  sim- 
ultaneously by  Mr.  Binney,  in  Lancashire,  and  by  Mr. 
Richard  Brown,  in  Cape  Breton,  and  it  has  been  con- 
firmed by  many  subsequently  observed  facts.  This  con- 
nection, when  once  established,  further  explained  the 
reason  of  the  almost  universal  occurrence  of  stigmaria, 
as  these  roots  were  called,  under  the  coal  beds;  while 
trunks  of  the  same  plants  were  the  most  abundant  fossils 


THE    SUN   THE   SOURCE    OF   ENERGY.  19 

of  their  partings  and  roofs.  The  growth  of  successive 
generations  of  sigillaria  was,  in  fact,  found  to  be  the 
principal  cause  of  the  accumulation  of  a  bed  of  coal." 

We  have  not  the  space  to  devote  to  the  numerous 
other  plants  found  in  coal  formation,  nor  to  the  success- 
ive cosmical  changes  winch  for  ages  have  buried  these 
plants  so  far  beneath  the  present  surface  of  the  earth, 
but  wish  to  show  that  the  sun  which  gave  to  these 
plants  both  light  and  heat  is  really  the  source  from 
whence  all  this  energy  is  derived. 

Prof.  Tyndall,  in  his  "  Heat  as  a  mode  of  motion " 
quotes  (section  707)  from  Sir  John  Hersnel,*  "The 
sun'a  rays  are  the  ultimate  source  of  almost  every 
motion  which  takes  place  on  the  surface  of  the  earth. 
By  its  heat  are  produced  all  winds,  and  those  distur- 
bances in  the  electric  equilibrium  of  the  atmosphere 
which  give  rise  to  the  phenomena  of  lightning,  and 
probably  also  to  terrestrial  magnetism  and  the  aurora. 
By  their  vivifying  action,  vegetables  are  enabled  to 
draw  support  from  inorganic  matter,  and  become  in 
their  turn  the  support  of  animals  and  man,  and  the 
source  of  those  great  deposits  of  dynamical  efficiency 
which  are  laid  up  for  human  use  in  our  coal-strata. 
By  them  the  waters  of  the  sea  are  made  to  circulate  in 
vapor  through  the  air,  and  irrigate  the  land,  producing 
springs  and  rivers.  By  them  are  produced  all  distur- 
bances of  the  chemical  equilibrium  of  the  elements  of 
nature,  which,  by  a  series  of  compositions  and  decom- 
positions, give  rise  to  new  products  and  originate  a 
transfer  of  materials.  Kveii  the  slow  gradation  of  the 
outlines  of  Astronomy,  1838. 


20  COMBUSTION    OF    COAL. 

solid  constituents  of  the  surface,  in  which  its  chief 
geological  change  consists,  is  almost  entirely  due,  on  the 
one  hand,  to  the  abrasion  of  wind  or  rain  and  the 
alternation  of  heat  and  frost;  on  the  other,  to  the  con- 
tinual heating  of  sea-waves  agitated  by  winds,  the 
results  of  solar  radiation." 

In  section  710  Prof.  Tyndall  says:  "In  the  building 
of  plants,  carbonic  acid  is  the  material  from  which  the 
carbon  of  the  plants  is  derived,  while  water  is  the  sub- 
stance from  which  it  obtains  its  hydrogen.  The  solar 
beam  winds  up  the  weight;  it  is  the  agent  which  severs 
the  atoms,  setting  the  oxygen  free,  and  allowing  the 
carbon  and  the  hydrogen  to  aggregate  in  woody  fibre. 

If  the  sun's  rays  fall  upon  a  surface  of  sand,  the  sand 
is  heated,  and  finally  radiates  away  as  much  heat  as  it 
receives ;  but  let  the  same  beams  fall  upon  a  forest ; 
then  the  quantity  of  heat  given  back  is  less  than  that 
received,  for  a  portion  of  the  sun-beams  is  invested 
in  the  building  of  the  trees.  Without  the  sun,  the 
reduction  of  the  carbonic  acid  and  water  can  not  be 
effected,  and,  in  this  act,  an  amount  of  solar  energy  is 
consumed  exactly  equivalent  to  the  molecular  work 
done." 

Dr.  Hermann  Vogel,  in  his  treatise  on  "The  chem- 
istry of  light  and  photography,"*  shows  the  chemical 
effect  of  sun-light  on  plants,  and  especially  the  modified 
growth  of  plants  owing  to  differences  in  the  intensity 
of  light.  He  says,  "  These  variations  in  the  chemical 
intensity  of  light  are  very  important  to  the  life  of 
plants.     The  green  leaves  of  plants  inhale  carbonic  acid 

*D.  Appleton  &  Co.,  N.  Y.,  1875. 


THE  SUN  THE  SOURCE  OF  ENERGY.  21 

and  exhale  oxygen  under  the  influence  of  light.  But 
this  breathing  process  does  not  take  place  without  the 
presence  of  light.  The  green  color  of  leaves  and  the 
variegated  scale  of  colors  in  flowers  exist  only  under 
the  operation  of  light.  In  the  dark,  plants  only  develop 
sickly  blossoms,  like  the  well  known  white  germs  of 
potatoes  kept  in  cellars. 

"The  necessity  of  light  for  the  life  of  plants  is  also 
seen  in  the  effort  made  by  plants  kept  in  darkened  rooms 
to  reach  the  apertures  which  admit  light,  growing,  as  it 
were,  toward  them.  Hence  a  plant  developes  with  an 
energy  proportioned  to  the  intensity  of  the  light. 
Accordingly,  the  greater  fruitfulness  of  the  tropics  is  to 
be  ascribed,  not  only  to  the  higher  temperature,  but  also 
to  the  greater  chemical  intensity  of  the  light.  Recent 
observations  have  established  that  the  yellow  and  red 
rays,  and  not  the  bine  and  violet,  produce  the  greatest 
chemical  effect* on  the  leaves  of  plants. 

"We  have  now  arrived  at  tin1  knowledge  of  the 
importance  of  light  for  the  economy  of  nature. 

"There  was  a  lime  when  the  atmosphere  was  richer 
in  carbonic  acid  gas  than  now.  When  the  incandescent 
and  fluid  masses  thai  once  formed  our  earth  gradually 
became  condensed,  when  the  watery  vapors  were  precip- 
itated as  seas,  the  atmosphere  contained  almost  all  the 
carbon  of  the  earth  after  combustion;  that  i-.  united 
with  oxygen  as  carbonic  acid  gas.  Tin'  air  was,  there- 
fore, at  that  time  infinitely  richer  in  carbouic  acid  than 
now.      When  at   length  the  earth  had  cooled   sufficiently 

for  vegetation  to  be  developed,  gigantic  plants  sho  I  forth 


22  COMBUSTION    OF    COAL. 

from  the  warm  ground  under  the  influence  of  the  sun- 
light. They  flourished  luxuriantly  in  the  atmosphere, 
rich  in  carbonic  acid,  the  carbon  of  the  carbonic  acid 
passed  over  into  the  form  of  wood,  and  thus  in  the  course 
of  thousands  of  years  it  was  continuously  diminished. 
Revolutions  of  the  earth's  surface  succeeded ;  whole  ter- 
ritories, with  their  forests,  were  buried  under  sand  and 
clay  beds,  and,  becoming  decomposed,  were  changed 
into  coal.  A  fresh  vegetation  sprouted  forth  from  the 
newly  formed  soil,  and  again  absorbed,  under  the  influ- 
ence of  light,  the  carbonic  acid  of  the  atmosphere,  to  be 
once  more  engulfed  by  a  fresh  cataclysm.  Thus  the  car- 
bonic acid  of  the  atmosphere  was  stored  as  coal  in  the 
depths  of  the  earth ;  and  thus  the  atmosphere,  by  the 
chemical  effects  of  light,  became  continually  richer  in 
oxygen,  until  at  length,  after  countless  revolutions  of  the 
earth,  it  obtained  that  wealth,  oxygen,  which  made  the 
existence  of  man  possible,  where  he  appeared  at  the 
end  of  the  earth's  development. 

"We  see,  therefore,  that  the  chemical  influence  of 
light  has  played  an  important  part  in  the  development 
of  our  planet,  and  it  continues  to  do  so  in  the  economy 
of  nature." 

Dissipation  of  Energy — If  we  attempt  to  carry  out  in 
practice  the  theory  that  any  form  of  energy  may  be 
transferred  into  another  form  without  loss  of  useful 
effect,  we  shall  be  sadly  disappointed.  This  has  been 
the  fruitless  field  so  long  cultivated  by  the  seekers  after 
a  perpetual  motion.  The  mistake  has  been  made  by 
them  in  this — in  supposing  that  the  various  forms  of 


DISSIPATION    OF    ENERGY.  23 

energy  may  be  transformed  into  mechanical  energy  or 
made  to  do  work  without  the  loss  incident  to  the  absorp- 
tion by  the  various  other  forms  of  energy  which  are 
contiguous,  and  which  are  constantly  seeking  fresh  sup- 
plies of  energy  from  a  source  higher  than  their  own. 
If  these  processes  were  not  only  transformable  but 
reversible,  then  perpetual  motion  would  be  a  met. 

We  know  that  heat,  as  a  form  of  visible  mechanical 
energy,  is  available  only  as  we  use  it  from  a  higher  to  a 
lower  temperature,  and  we  know  further,  that,  once  the 
licat  has  spent  its  energy  or  capacity  for  doing  work, 
there  is  no  way  by  which  it  can  be  restored.  Heat  may 
be  made  to  do  work,  and  work  may  be  transferred  into 
heat,  but  the  processes  are  not  reversible. 

Tins  does  not  in  the  least  invalidate  what  is  known 
as  the  mechanical  equivalent  of  heat,  for  it  takes  into 
account  all  the  losses  incident  to  the  transfer  of  availa- 
ble energy,  but  the  transfer  once  made,  complete  restor- 
ation is  impossible. 

In  all  cases  there  is  a  tendency  for  the  useful  energy, 
whenever  a  transformation  takes  place,  (28)  to  run  down 
in  the  scab — that,  the  quantity  being  unaltered,  the 
quality  becomes  deteriorated,  or  the  availability  becomes 
less;  and  from  similar  results  in  all  branches  of  physics 
we  are  entitled  to  enunciate,  as  Sir  William  Thompson 
did  very  early  after  the  new  ideas  were  brought  into 
full  development,  the  principle  of  dissipation  of  energj 
in  nature. 

The  principle  of  dissipation,  or  degradation,  as  I 
3hould  prefer  to  call  it,  is  simply  this,  that  as  any  opera- 


24  COMBUSTION    OF    COAL. 

tion  going  on  in  nature  involves  a  transformation  of 
energy,  and  every  transformation  involves  a  certain 
amount  of  degradation  (degraded  energry  meaning: 
energy  less  capable  of  being  transformed  than  before), 
energy  is  continually  becoming  less  and  less  trans- 
formable. 

As  long  as  these  changes  are  going  on  in  nature,  the 
energy  of  the  universe  is  getting  lower  and  lower  in  the 
scale,  and  you  can  see  at  once  what  its  ultimate  form 
must  be,  so  far,  at  all  events,  as  our  knowledge  yet 
extends.  Its  ultimate  form  must  be  that  of  heat  so 
diffused  as  to  give  all  bodies  the  same  temperature. 
Whether  it  be  a  high  temperature  or  a  low  temperature 
does  not  matter,  because  whenever  heat  is  so  diffused  as 
to  produce  uniformity  of  temperature,  it  is  in  a  condi- 
tion from  which  it  can  not  raise  itself  again.  In  order 
to  get  any  work  out  of  heat,  it  is  absolutely  necessary 
to  have  a  hotter  body  and  a  colder  one;  but  if  all  the 
energy  in  the  universe  be  transformed  into  heat,  and  if 
it  be  in  all  bodies  at  the  same  temperature,  then  it  is 
impossible — at  all  events  by  any  process  we  know  of  as 
yet — to  raise  the  smallest  part  of  that  energy  into  a 
more  available  form. 


CHAPTER   II. 

THE  ATMOSPHERE. 

Air  the  Source  of  Oxygen  for  Combustion — Composition  of  the 
Air — Nitrogen — The  Chemical  Compounds  of  Oxygen  and 
Nitrogen — Properties  of  Oxygen — The  Physical  Properties  of 
the  Atmosphere — Absorption  of  Moisture — Cause  of  Pain — 
Radiation  of  Heat  through  the  Air — Carbonic  Acid  and 
Ammonia  in  the  Air — Ozone. 

Atmospheric  Air — The  source  of  oxygen,  as  a  sup- 
porter of  furnace  combustion,  is  atmospheric  air.  The 
exact  compositioD  of  the  atmosphere  has  been  made  the 
subject  of  experimental  research,  and  from  samples 
taken  a1  different  heights  above  the  level  of  the  sea,  as 
well  as  depths  below  it;  from  nearly  every  quarter  of 
the  globe;  analysis  .show  it  to  be  essentially  the  same. 
The  height  of  the  atmosphere  has  not  been  accurately 
determined,  but  it  is  supposed  to  be  about  forty-five 
miles.  The  pressure  of  the  atmosphere  is  one  of  its 
mosi  important  properties,  not  only  in  the  ordinary 
economy  of  nature,  but  as  a  mechanical  agency  in  pro- 
ducing draught  in  the  furnace.  The  measured  quantity 
id'  this  pressure  is  found  to  be  equal  to  a  column  of 
mercury  having  one  square  inch  of  area  by  thirty  inches 
in  height,  or,  taking  the  weight  of  the  mercury  instead, 
we  then  have  14.73  lb.  as  the  weight  of  the  atmosphere; 
subject,  however,  to  changes  of  temperature,  humidity, 
etc.  In  all  ordinary  calculations  it  is  assumed  that  32 
feel  of  water.  •■;<>  inches  of  mercury  or  1">  lbs.  equal  the 
pressure  of  the  atmosphere. 


26  COMBUSTION   OF    COAL. 

Air  was  long  believed  to  be  simple  substance,  and 
when  its  composite  nature  was  discovered,  and  it  was 
found  to  be  a  combination  of  nitrogen  and  oxygen,  the 
first  supposition  was  that  the  union  was  a  chemical  one, 
but  farther  research  showed  the  mixture  to  be  mechan- 
ical. We  have  already  stated  that  when  two  bodies 
unite  with  each  other  chemically,  the  product  of  this 
combination  is  a  compound  differing  from  the  elements 
of  which  it  is  composed.  The  union  of  these  two  gases 
in  the  proportions  approximating  four  volumes  of  nitro- 
gen to  one  of  oxygen  gives  common  air,  and  this  union 
is  distinguished  by  no  properties  which  may  not  be 
attributed  individually  to  these  gases. 

From  this  circumstance,  not  alone,  but  from  the  fact 
that  every  experiment  to  determine  whether  this  union  is 
a  chemical  one,  there  has  been  so  far  no  indication  that 
the  union  is  other  than  mechanical. 

The  composition  of  atmospheric  air  varies  in  differ- 
ent localities,  owing  to  local  causes,  but  these  changes 
are  so  minute  that  it  is  extremely  difficult  to  detect  com- 
bining gases.  A  mean  composition  of  atmospheric  air 
shows  it  to  be  composed  of, 

VOLUME. 
PKK    CENT. 

Nitrogen 79 

Oxygen 21 

100 
Aqueous  vapor  is  present  in  the  air  at  all  times,  even 

at  the  lowest  temperatures  yet  observed. 

From  three  to  ten  volumes  of  carbonic  acid  in  ten 

thousand  parts  of  air  have  also  been  observed. 


NITROGEN.  27 


The  weight  of  one  cubic  foot  of  air  at  32°  Fahr.  is 
.080728  lb.  or  565.1  grains;  at  62°  it  is  .076097  lb.  or  532.7 
grains.  The  volume  of  one  pound  of  air  at  32°  Fahr. 
at  ordinary  atmospheric  pressure  (14.7  lbs.)  is  12.4  cubic 
feet. 

Nitrogen — By  volume  and  by  weight  nitrogen  is  the 
principal  constituent  of  the  atmosphere;  it  is  colorless, 
and  a  little  lighter  than  the  air;  the  specific  gravity  of 
air  being  1.0000,  that  of  nitrogen  is  .9736.  It  is  not  a 
supporter  of  combustion,  and  its  negative  qualities  are 
so  gracefully  given  by  Professor  Faraday  in  his  lectures 
on  "The  Chemical  History  of  a  Candle,"  that  I  quote: 
*k  Tliis  other  part  of  the  air  is  by  far  the  larger  portion, 
and  it  is  a  very  curious  body  when  we  come  to  examine 
it;  it  is  remarkably  curious,  and  yet  you  say,  per- 
haps, that  it  is  very  uninteresting.  It  is  uninteresting 
in  some  respects  because  of  this,  that  it  shows  no  bril- 
liant effects  of  combustion.  If  I  test  it  with  a  taper  as 
I  do  oxygen  and  hydrogen,  it  does  not  burn  like  hydro- 
gen, nor  does  it  make  the  taper  burn  like  oxygen.  Try 
it  in  any  way  I  will,  it  does  neither  the  one  thing  nor 
tlic  oilier;  it  will  not  take  tire;  it  will  not  let  the  taper 
burn;  it  puts  out  the  combustion  of  everything.  There 
is  nothing  that  will  burn  in  it  in  common  circumstances. 
Et  has  no  smell;  it, is  not  sour;  it  does  not  dissolve  in 
water;  it  is  neither  an  acid  nor  an  alkali;  it  is  as  indif- 
ferent to  all  our  organs  as  it  is  possible  for  a  thing  to  be. 
And  you  might  say,  'It  is  nothing;  it  is  not  worth 
chemical  attention;  what  does  it  do  in  the  air?' 


28  COMBUSTION    OF    COAL. 

"Ah !  then  come  our  beautiful  and  fine  results  shown 
by  an  observant  philosophy.  Suppose,  in  place  of  having 
nitrogen,  or  nitrogen  and  oxygen,  we  had  pure  oxygen  as 
our  atmosphere ;  what  would  become  of  us?  You  know 
very  well  that  a  piece  of  iron  lit  in  a  jar  of  oxygen  goes 
on  burning  to  the  end.  When  you  see  a  fire  on  an  iron 
grate,  imagine  where  the  grate  would  go  to  if  the  whole 
of  the  atmosphere  were  oxygen.  The  grate  would  burn 
up  more  powerfully  than  the  coals;  for  the  grate  itself 
is  even  more  combustible  than  the  coals  which  we  burn 
in  it.  A  fire  put  into  the  middle  of  a  locomotive  would 
be  a  fire  in  a  magazine  of  fuel,  if  the  atmosphere  were 
oxygen.  The  nitrogen  lowers  it  down  and  makes  it 
moderate  and  useful  for  us,  and  then,  with  all  that,  it 
takes  away  with  it  the  fumes  you  have  seen  produced 
from  the  candle,  dispenses  them  throughout  the  whole 
of  the  atmosphere,  and  carries  them  away  to  places 
where  they  are  wanted  to  perform  a  great  and  glorious 
purpose  of  good  to  man,  for  the  sustenance  of  vegeta- 
tion, and  thus  does  a  most  wonderful  work,  although 
you  say,  on  examining  it,  'why,  it  is  a  perfectly  indif- 
ferent thing.'  This  nitrogen  in  its  ordinary  state  is  an 
active  element;  no  action  short  of  the  most  intense 
electric  force,  and  then  in  the  most  infinitely  small 
degree,  can  cause  the  nitrogen  to  combine  directly  with 
the  other  element  of  the  atmosphere,  or  with  things 
round  about  it;  it  is  perfectly  indifferent,  and  therefore 
to  say,  a  safe  substance." 

It  will  be  seen  from  the  above  that  nitrogen  plays 
no  active  part  whatever  in  combustion — it  is  simply  the 


OXYGEX. 


29 


vessel,  so  to  speak,  in  which  the  oxygen  is  delivered; 
the  delivery  having  been  made  the  vessel  is  no  longer 
of  any  value  in  that  connection,  but  the  delivery  is 
made  in  the  body  of  incandescent  fuel,  and  after  its 
separation  from  the  oxygen  it  passes  on  through  the 
fire,  and  by  virtue  of  its  lighter  gravity  assists  in  main- 
taining a  good  draught,  a  matter  of  prime  importance 
in  furnace  combustion. 

Nitrogen  combines  with  oxygen  to  form  five  distinct 
compounds,  us  below: 

Table  III. 


SYMBOL. 

COMPOSITION. 

NAME. 

WEIGHT. 

VOLUME. 

NITROGEN. 

OXYGEN. 

NITROGEN. 

OXYGEN. 

Nitrogen  monoxide.... 

N,  0 

28 

16 

2 

1 

Nitrogen  dioxide 

\    <  i . 

28 

32 

2 

2 

N '.    "; 

28 

48 

2 

3 

Nitrogen  tetroxide 

N,  0, 

28 

04 

•) 

4 

Nitrogen  pentoxide.... 

N .,  ( »., 

28 

80 

2 

5 

Oxyr/cn  is  somewhat  heavier  than  the  air,  having  a 
Bpecific  gravity  of  1.1056,  air  being  1.0000.  It  is  the 
most  abundant  of  all  the  elements :  it  forms  eight -ninths 
of  water;  uearly  one-fourth  of  air;  and  about  one-half 
of  silica,  chalk  and  alumina;  the  three  most  plentiful 
constituents  of  tic  earth's  surface.  Oxygen  when  free 
or  uncombined  is  known  only  in  the  gaseous  Btate. 
Numerous  attempts  have  beeu   made  to  reduce  it  to  a 


30  COMBUSTION   OF    COAL. 

liquid   or  solid   state,  but  so  far  the  efforts  have  been 
fruitless. 

Oxygen  when  pure  is  colorless,  tasteless  and  ino- 
derous.  It  combines  with  every  known  substance 
except  fluorine.  It  is  essential  to  the  support  of  animal 
life,  and  is  the  sustaining  principle  of  all  the  ordinary 
phenomena  of  combustion;  and  there  are  few  experi- 
ments more  brilliant  than  the  burning  of  phosphorus, 
carbon  or  iron,  in  this  gas,  the  products  in  each  case 
being  oxydized  compounds  of  the  substances  burned. 
The  weight  of  any  compound  will  be  found  to  be  in  all 
cases  equal  to  the  weight  of  the  body  burned,  added  to 
the  weight  of  the  oxygen  required  to  effect  the  change. 

The  Physical  Properties  of  the  Atmosphere  (25)* — 
"Air,  although  essentially  an  invisible  substance,  has 
weight.  A  room  the  size  of  Westminster  hall  con- 
tains as  much  as  seventy-five  tons  of  air.  The  atoms 
of  the  air  are  of  a  minuteness  that  is  perhaps  quite 
inconceivable  by  the  human  mind.  They  are  much 
smaller  than  the  minutest  molecules  that  can  be  made 
visible  by  the  microscope,  and  have  a  breadth  of  about 
the  3^5-  in.  They  exist  in  what  is  termed  the  gaseous 
state,  which  means  that,  small  as  they  are,  they  float 
many  of  their  own  diameters  asunder,  from  which  it 
arises  that  air  is  compressible  by  the  application  of 
mechanical  force.  By  a  pressure  of  fifteen  lbs.  upon 
each  square  inch,  air  is  reduced  to  half  its  previous 
bulk,  although  water,  by  the  same  pressure,  is  only 
compressed   the  ^  part.     Mariotte   and   Boyle   have 

-From  a  lecture  by  Dr.  Maun,  London. 


WEIGHT    OF   THE    ATMOSPHERE.  31 

established  the  law  that  every  time  the  pressure  upon 
air  is  doubled  its  volume  is  halved.  This  is  the  obvious 
reason  why  the  air  is  more  rare  and  light,  bulk  for  bulk, 
at  the  higher  regions  of  the  atmosphere,  than  it  is  near 
the  surface  of  the  earth.  But  it  is  also  expanded  by 
increase  of  temperature,  and  this  also  by  a  fixed  law, 
which  is,  that  air  is  increased  in  volume  -^  part  for  each 
degree  Fahr.;  one  thousand  cubic  inches  at  freezing  tem- 
perature are  increased  to  1366.5  inches  at  the  boiling 
point.  The  rarefaction  of  the  atmosphere  with  ascent 
toward  the  higher  regions  is  also  affected  according 
to  a  fixed  law ;  at  a  height  of  three  miles  the  air  has  a 
doubled  volume  and  half  its  original  density;  it  is 
again  doubled  in  volume  at  about  six  miles  high.  It 
is  probable  that  no  animal  could  continue  to  live  and 
breathe  at  a  height  of  eight  miles.  The  actual  outer 
limit  of  the  atmosphere  is  not  certainly  known. 

"  Wi  ight  of  the  Atmosphere — The  weight  of  the  entire 
atmosphere  was  first  demonstrated  by  Torricelli  when 
he  made  his  memorable  invention  of  the  barometer. 
It  amounts  to  the  same  as  the  weight  of  a  column  of 
mercury  of  the  same  diameter,  thirty  inches  high.  But 
mercury  is  eleven  thousand  time-  heavier  than  an  equal 
bulk  of  air.  There  is  nearly  one  ton  weight  of  air  on 
each  square  foot  of  the  ground.-  The  atmosphere 
amounts  to  about  the  .  ±-  part  of  the  weight  of  the 
entire  earth.  Air,  however,  presses  in  all  directions  as 
well  as  down.  The  air  is  really  composed  of  two  dif- 
ferent  kinds  of  gasses,  which  mingle  wit hoiit   interfer- 


32  COMBUSTION    OF    COAL. 

ing  with,  each  other  by  pressure.     Each  is,  as  it  were. 
a  vacuum  to  the  other. 

"  Vapor — The  vapor  of  water  rises  into  the  inter- 
spaces of  these  aerial  atoms  in  a  similarly  free  and 
unconstrained  way;  hut  more  of  it  can  be  sustained  in 
warm  air  than  in  cold.  Air  at  a  temperature  of  32° 
can  sustain  the  ~  part  of  its  own  weight  of  aqueous 
vapor,  but  at  86°  it  can  sustain  ~  part  of  its  own 
weight.  The  barometer  gives  the  combined  weight  of 
the  oxygen,  nitrogen,  and  gaseous  vapor  of  the  air,  and 
the  portion  of  this  weight  which  is  due  to  aqueous  va- 
por is  called  the  elastic  force  of  vapor.  With  a  barom- 
eter standing  at  30.000  inches,  and  with  a  hygrometer 
indicating  an  elastic  force  of  vapor  of  0.450,  very  nearly 
one-quarter  lb.  of  the- entire  pressure  of  fifteen  lbs.  on 
each  square  inch  is  due  to  the  vapor.  When  more 
vapor  is  generated  than  can  be  at  once  carried  away, 
the  barometer  necessarily  rises ;  when  vapor  is  con- 
densed in  the  atmosphere,  the  barometer  falls;  when 
the  temperature  of  saturated  air  is  reduced  from  80°  to 
60°,  five  grains  of  aqueous  vapor  are  deposited  from 
each  cubic  foot.  This  is  the  effective  cause  of  rain. 
Warm  air  drinks  up  vapor  and  carries  it  away,  and 
subsequently  deposits  it  when  it  comes  to  some  region 
where  it  gets  chilled. 

"The  Temperature  of  the  air  decreases  with  height, 
about  1°  for  each  three  hundred  feet  or  four  hundred 
feet  ascended;  this  is  because  the  air  gets  further  from 
the  source  of  heat,  and  also  because  heat  is  absorbed 


CARBONIC    ACID. 


above  to  maintain  the  expansion  of  the  air.  Sensible 
heat  is  lost  on  the  expansion  of  air,  and  is  produced, 
on  its  condensation.  Pure  air  is  virtually  quite  per- 
vious to  heat;  none  stops  in  the  air,  but  all  passes 
through.  Aqueous  vapor,  on  the  other  hand,  acts  as. 
a  screen  to  heat.  Prof.  Tyndall  has  shown  that  ten  per 
cent,  of  the  solar  heat  radiated  from  the  earth  through 
a  moist  atmosphere  is  stopped  within  ten  feet  of  the- 
ground.  The  absolute  diathermancy  of  dry  air  ac- 
counts for  the  scorching  heat  of  mountain  tops,  as  the 
retentive  power  of  aqueous  vapor  does  for  the  soft  heat 
of  low  lying  regions  in  the  tropics.  The  rain  deluges 
of  equatorial  calms  are  due  to  the  radiation  of  heat 
through  the  upper  dry  layers  of  the  atmosphere. 
Cumuli  clouds  arc  formed  from  the  same  cause;  they 
are  the  capitals  of  invisible  columns  of  saturated  air. 
Mountain  tops  are  condensers  of  moisture  for  a  similar 
reason. 

"  Carbonic  Acid — There  is  in  air,  besides  the  aqueous 
vapor,  3.36  parts  in  every  ten  thousand  of  carbonic 
acid  gas.  and  three  and  a-half  parts  in  every  ten  mill- 
ions of  ammonia.  Small  as  these  quantities  appeal'. 
they  are  sufficient  to  produce  very  astonishing  results; 
there  are  one  million  three  hundred  thousand  tons  of 
carbonic  acid,  containing  three  hundred  and  seventy- 
one  thousand  tour  hundred  and  seventy-five  tons  of 
carbon  in  the  air,  which  rests  upon  each  square  mile 
of  the  earth,  and  thirty  lbs.  of  ammonia  arc  carried 
down  by  the  rain  to  each  acre  of  land  every  year. 
(4) 


34  COMBUSTION    OF    COAL. 

"  Ozone— There  is  one  part  of  ozone  in  every  seven 
hundred  parts  of  air;  but  this  ozone  is  in  reality  only 
a  condensed  form  of  oxygen  itself;  three  volumes  of 
oxygen  are  condensed  to  form  two  volumes  of  ozone. 
It  is  oxygen  in  an  increased  state  of  activity. 

"  The  Diathermancy  and  Transparency  of  the  air  are 
both  of  the  very  highest  importance  to  the  life  existing 
upon  the  earth.  It  is  its  diathermancy  which  enables 
the  sun's  heat  to  reach  the  terrestrial  surface  for  the 
performance  of  its  marvelous  operations.  It  is  its  trans- 
parency which  renders  the  air  the  window  of  the  earth, 
giving  man  his  outlook  into  space  and  admitting  the 
wonderful  effects  of  color  and  light.  If  the  air  were 
not  transparent,  all  nature  would  be  in  a  perpetual 
dense  fog.  The  blueness  of  the  sky  is  due  to  the  weak 
blue  rays  of  light  being  arrested  by  the  air  and  its 
transparent  vapors,  and  turned  back  upon  the  earth. 
The  brilliant  sun-set  colors  are  similarly  due  to  the 
arrest  and  reflection  of  the  stronger  yellow  and  red 
vibrations,  by  the  denser  vapors  of  the  clouds." 


CHAPTER    III. 


FUELS. 

Classification  of  Fuel — Wood. — Water  Present  in  Wood — Composi- 
tion of  Wood  —  Wood  Charcoal  —  Combustibility  of  Wood 
Charcoal — Peat — Analysis  of  Peat — Products  of  the  Distilla- 
tion of  Peat — Peat  as  a  Fuel — Peat  Charcoal — Lignite — Differ- 
ence between  Lignite  and  Brown  Coal — Lignite  as  a  Fuel — 
Water  in  Lignite — Analysis  of  Lignites — Classification  of  Coal 
— Bituminous  Coal — Analysis  of  Bituminous  Coals — Non-caking 
Coals — Block  Coal — Caking  Coals — Gas  Coal — Coke — The  Influ- 
ence of  Temperature  and  Pressure  in  the  yield  of  Coke — Can- 
nel  Coal  —  Semi-bituminous  Coal  —  Semi-anthracite  Coal  — 
Anthracite  Coal. 

Fuel  is  a  word  employed  to  express,  in  general 
terms,  any  substance  which  may  be  economically  burned 
by  means  of  atmospheric  air  to  generate  heat.  The 
economic  value  of  any  fuel  will  depend  upon  its  heating 
power.  The  two  elements  contributing  this  property 
to  fuel  are  carbon  and  hydrogen.  The  more  impor- 
tant varieties  of  fuel  include  wood,  peat,  lignite  and 
coal.     These  are  classed  by  Dr.  Percy  as  follows: 


Classification  ok  Fuels. 
Wood. 


Peat. 


Coal. 


f  Non-caking,  rich  in  oxygen. 
Bituminous.    1   Caking. 
Anthracite.      I  Non-caking  rich  in  carbon. 


36 


COMBUSTION    OF    COAL. 


Carbonization. 

Products  of 


Wood — charcoal. 
Solid.        i   Peat — charcoal. 
[  Coke. 

f  Carbonic  Oxide. 
Volatile.  J   Hydrogen. 

Hydro-carbon. 


Wood,  as  a  fuel,  may  be  divided  into  two  classes, 
hard  and  soft. 

Hard  woods  include  compact,  heavy  woods — like 
oak,  hickory,  heech,  elm,  ash,  walnut. 

Soft  woods  include  pine,  birch,  poplar,  willow. 

Freshly  cut  green  wood  contains  on  an  average 
about  forty-five  per  cent,  of  moisture,  often  more, 
though  sometimes  less;  and  after  long  exposure  to  the 
atmosphere  under  favorable  conditions  it  still  retains 
from  eighteen  to  twenty  per  cent,  of  moisture.  This  is 
a  point  of  great  practical  importance  in  reference  to  the 
direct  application  of  wood  as  fuel.  The  following  table, 
prepared  by  M.  Violette,  shows  the  proportion  of  water 
expelled  from  wood  at  gradually  increasing  tempera- 
tures : 

Table  IV. 


TEMPERATURE. 

WATER  EXPELLED   FROM  ONE  HUNDRED 
PARTS  OF  WOOD. 

OAK. 

ASH. 

ELM. 

WALNUT. 

257°  Fahr 

15.26" 
17.93 
32.13 
35.80 
44.31 

14.78 
16.19 
21.22 
27.51 

33.38 

15.32 
17.02 
36.94? 

OO.OO 

40.56 

15.55 

30°°  Fahr 

17.43 

347°  Fahr 

21.00 

392°  Fahr  

41.77? 

437°  Fahr 

36.56 

THE    COMPOSITION    OF    WOOD. 


37 


The  wood  which  M.  Violette  operated  upon  had 
been  kept  in  store  during  twTo  years. 

In  each  experiment  the  specimens  were  exposed 
during  two  hours  to  dessication  in  a  current  of  super- 
heated steam,  of  which,  the  temperature  was  gradually 
raised  from  257°  to  437°  Fahr.  "When  wood,  which  has 
been  strongly  dried  by  means  of  artificial  heat,  is  left 
exposed  to  the  atmosphere,  it  re-absorbs  about  as  much 
water  as  it  contains  in  its  air-dried  state. 

Tablk  V — Showing  The  Composition"  of  Wood. 
ANALYSIS  BY  M.  EUGENE  CHEVANDIEB. 


WOODS. 

COMPOSITION 

CARBON. 

HYDROGEN 

OXYGEX. 

NITROGEN. 

ASH. 

Beech 

PER  CEXT. 

49.36 
49  64 
50.20 
49.37 
49.96 

PER  CEXT. 

6.01 

5.92 
6.20 
6.21 
5.96 

PER  CEXT. 

42.69 

41.16 
41.62 
41.60 
39.56 

PER  CEXT. 

0.91 
1.29 
1.15 

0.96 
0.96 

PER  CEXT. 
1.00 

Oak 

Birch 

1.97 
0.81 

Poplar 

1.86 

Willow 

3.37 

A  vt-riige 

49.711 

6.06 

41.30 

1.05 

1.80 

Where  wood  is  protected  from  the  atmosphere  and 
heated  to  about  600°  Fahr.,  its  gaseous  or  volatile 
element-  are  driven  off",  and  a  fixed  residue  called  char- 
coal remains. 

<! 1  charcoal   is  black;  gives  a  sonorous  ring  when 

-i nick;  breaks  with  more  or  less  conchoidal  fracture; 
is  easily  pulverizable,  but  does  not  crumble  under  mod- 


38 


COMBUSTION    OF    COAL. 


erate  pressure;  floats  on  water,  and  does  not  burn  with 
flame  when  ignited  in  separate  pieces. 

Table  VI — Showing  the  Composition"  op  Charcoal  Produced  at 
Various  Temperatures  (2). 

BY  M,  VIOLETTE. 


TEMPERATURE 

COMPOSITION    OF   THE   SOLID    PRODUCT. 

o     o 

h  S3  H 

OF 
CARBONIZATION. 

CARBON. 

HYDROGEN 

OXYGEN, 
NITROGEN 
AND  LOSS. 

ASH. 

B  O  W  C 

FAHRENHEIT. 
302°    1    

PER  CENT. 

47.51 

51.82 
65.59 
73.24 
76.64 
81.64 
81.97 
83.29 
88.14 
90.81 
94.57 
96.52 

PER  CENT. 

6.12 
3.99 
4.81 
4.25 
4.14 
4.96 
2.30 
1.70 
1.42 
1.58 
0.74 
0.62 

PER  CENT. 

46.29 

43.98 

28.97 

21.96 

18.44 

15.24 

14.15 

13.79 

9.26 

6.49 

3.84 

0.94 

PER  CENT. 

0.08 
0.23 
0.63 
0.57 
0.61 
1.61 
1.60 
1.22 
1.20 
1.15 
0.66 
1.95 

PER  CENT. 
47.51 

392*  J     

39.88 

482 

32.98 

572 

24.61 

662 

22  42 

810 

15.40 

1873 

15.30 

2012 

15.32 

2282 

15.80 

2372 

15.85 

2732 

16.36 

Melting  point  of) 

14.47 

The  wood  experimented  on  was  that  of  black  alder 
or  alder  buckthorn,  which  furnishes  a  charcoal  suitable 
for  gunpowder. 

Combustibility  of  Wood-charcoal — M.  Violette  states 
that  charcoal  made  at  500°  Fahr.  burns  most  easily;  and 
that  made  between  1832°  and  2732°  Fahr.  can  not  be 

*  The  products  obtained  at  these  temperatures  can  not  properly  be  termed 
charcoal. 


PEAT    OR    TURF.  39 


ignited  like  ordinary  charcoal.  Charcoal  made  at  a 
constant  temperature  of  572°  Fahr.  takes  fire  in  the  air 
when  heated  to  between  680°  and  716°  Fahr.,  according  to 
the  nature  of  the  wood  from  which  it  has  been  derived; 
charcoal  from  light  woods,  other  things  he  equal,  ignit- 
ing most  easily. 

Peat  or  Turf — Feat  is  composed  of  various  kinds 
of  plants  which  are  undergoing  a  gradual  trans  orraa- 
tion  by  a  process  of  slow  burning  or  carbonization,  in 
which  the  oxygen  of  the  plants  is  being  liberated  under 
special  conditions  of  moisture  and  heat,  leaving  a 
spongy  carbonaceous  mass,  in  which  the  remains  of  the 
plants  are  often  so  well  preserved  that  species  may 
easily  be  distinguished.  The  formation  of  peat  may  be 
regarded  as  one  of  the  most  important  geological 
changes  now  in  evident  progress.  Immense  accumula- 
tions of  peat  exist  in  various  parts  of  the  world. 
Within  two  miles  of  South  Bend,  Indiana,  is  the  eastern 
terminus  of  one  of  the  most  extensive  peat  beds  known, 
(4)  being  three  miles  in  width  and  extending  westward 
down  the  valley  of  the  Kankakee  for  more  than  sixty 
miles,  varying  from  five  to  fifty  feet  in  thickness. 

In  color,  peat  varies  from  a  yellowish-brown  through 
all  gradations  to  a  very  dark  brown,  almost  black.  The 
former  in  structure  is  light,  spongy  and  fibrous;  the 
latter  is  more  compact  and  pitchy  in  its  appearance,  the 
fibrous  texture  being  almost  entirely  obliterated.  In 
advanced  stages  of  decomposition  it  is  compact  ami 
dense,  presenting  an  earthy  fracture  when  broken;  in 
general  the  darker  the  peat  the  richer  it  is  in  carbon. 


40 


COMBUSTION    OF    COAL. 


Peat  formations  are  confined  to  cold  and  temperate 
climates,  and  swampy  ground.  In  its  natural  and  more 
advanced  state,  peat  contains  about  three-fourths  of  its 
own  weight  of  water;  in  the  earlier  stages  of  decompo- 
sition the  quantity  of  water  present  often  amounts  to  as 
much  as  ninety  per  cent,  of  the  whole  weight,  and  is 
totally  unfit  for  any  of  the  purposes  for  which  fnel  is 
employed. 

Very  little  use  has  been  made  of  peat  in  this  country, 
owing  to  the  abundance,  cheapness  and  superior  heat- 
ing power  of  coal.  In  Ireland,  Grermany,  Sweden  and 
oilier  foreign  countries,  it  is  used  largely  not  only  for 
domestic,  but  for  metallurgical  purposes. 

The  following  analysis  of  Irish  peat  is  upon  the 
authority  of  Sir  Robert  Kane : 


Table  VII — Chemical  Composition'  of  Irish  Peat  (2). 

PERFECTLY  DRY. 


DESCRIPTION    AND   LOCALITY 
OF   PEAT. 

£  < 
.V.  - 

X 

© 

B 

O 

5 

K 
O 

© 

a 
o 
o 

« 

a 

< 

.405 

.669 

.335 

.655 
.500 
.280 
.853 

PER 

CENT. 

57.52 
58.56 
58.30 
56.34 
58.60 
58.53 
59.42 

PER 
CENT. 

6.83 

5.91 
6.4:; 
4.81 
6.55 
5.73 
5.49 

PER 
CENT. 

32.23 
31.40 
31.36 
30.20 
30.50 
32.32 
30.50 

PER 
CENT. 

1.42 
0.85 
1.22 
0.74 
1.84 
0.93 
1.64 

PER 
CENT. 

1.99 

3.30 

2.74 

I.    Compact  and  dense,  Wood  of  Allen... 

7.90 
2.63 

2.47 

7.    Very  dense,  compact, Upper  Shan'on 

2.97 

.528 

58.18 

5.96 

31.21 

1.23 

3.43 

DISTILLATION    OF    IRISH    PEAT; 


41 


Table  VIII — Showing  the  Products  of  Distillation  of  the    Irish 
Peats  given*  in  Table  No.  VII. 


DESCRIPTION  AND  LOCALITY  OF 
PEAT. 

WATER. 

CRUDE  TAR. 

CHARCOAL. 

GAS. 

Nos.  1  and  2.  Philipstown 

No  3  Wood  of  Allen 

PER  CENT. 

23.6 
32.3 
38.1 
33.6 
38.1 
21.8 

PER  CENT. 

2.0 
3.6 
2.8 
2.9 
4.4 
1.5 

PER  CENT. 

37.5 
39.1 
32.6 
31.1 
21.8 
19.0 

PER  CENT. 

36.9 
25.0 

\o  4   Wood  of  Allen 

26.5 

No   5  Tickneven 

32.:; 

So   7  Upper  Shannon 

35.7 
57.7 

A  vera  ges 

31.4 

2.8 

29.2 

36.6 

The  tar,  when  re-distilled,  yielded  water,  paraffine, 
oils,  charcoal  and  gas. 

The  water  yielded  chloride  of  ammonium,  acetic 
acid  and  wood-spirit. 

In  a  French  report  on  the  use  of  peat  as  a  fuel  for 
locomotives,  after  experimenting  on  a  large  scale,  the 
conclusion  was  reached  that  an  economy  of  nearly  one- 
half  might  be  effected  over  a  similar  mileage  and  ton- 
age  with  coal;  setting  aside  the  greatly  reduced  injury 
to  boilers,  dues  and  grates.  It  is  also  claimed  for  peat 
in  this  report  that,  the  firing  once  understood,  is  much 
more  easily  managed  than  coal;  requiring  no  stokim:: 
tie-  heal  being  more  regular,  and  not  subject  to  the  Bud- 
. leu  changes  in  intensity  that  occur  so  frequently  with 
coal  and  coke,  and  which  changes  injure  the  furnaces. 


42  COMBUSTION   OF    COAL. 

Peat  Charcoal — The  charcoal  produced  by  the  car- 
bonization of  ordinary  air-dried  peat  is  very  friable  and 
porous ;  it  takes  ■  fire  very  readily,  and  when  ignited 
nearly  always  continues  to  burn  until  its  carbonaceous 
matter  is  wholly  consumed ;  it  scintillates  in  a  remarka- 
ble degree  when  burned  in  a  smith's  fire;  its  extinction 
when  in  mass  is  difficult,  and  hence  this  is  the  trouble- 
some part  of  its  manufacture  by  the  usual  method  of 
carbonization  in  piles;  and  it  is  so  little  coherent  that 
it  can  not  be  conveyed  without  much  of  it  being 
crushed  to  dust  (20). 

Lignite — Is  classed  among  mineral  coals,  and  occu- 
pies a  position  historically  between  peat  and  bituminous 
coal.  It  is  not  synonymous  with  brown  coal,  proper, 
though  there  are  many  points  of  similarity.  It  is  believed 
to  be  of  later  origin  than  bituminous  coal  and  is  in  a  less 
advanced  stage  of  decomposition ;  the  woody  fibre  and 
vegetable  texture  of  lignite  is  almost  entirely  wanting 
in  coal,  though  there  is  little  doubt  that  they  are  of  one 
common  origin.  The  chemical  difference  between  lignite 
and  brown  coal  may  be  determined  by  dry  distillation, 
in  which  the  former  yields  acetic  acid,  and  acetate  of 
ammonia,  whereas,  coal  produces  only  ammonical  liquor 
(5).  "Woody  fibre  gives  rise  to  acetic  acid;  lignite 
must,  therefore,  still  contain  undecomposed  woody  fibre. 
Lignite  and  brown  coal  belong  chiefly  to  the  cretaceous 
and  tertiary  periods.  Lignite  varies  considerably  in 
appearance  and  structure,  usually,  however,  preserving 
a  wood-like  appearance  when  broken,  the  fracture  is 
uneven  presenting  a  brown  to  a  very  dark  brown-black 


LIGNITE.  .  43 

color,  with  a  dull  and  frequently  a  fatty  lustre.  It 
easily  breaks  or  crumbles  in  handling,  and  will  not  bear 
rough  transportation  to  great  distance;  neither  will  it 
bear  long  continued  exposure  to  the  weather;  crumbling 
rapidly. 

It  can  be  coked  but  the  coke  is  not  of  good  quality, 
though  some  lignites  coke  better  than  others. 

As  a  fuel  it  must  be  used  in  its  natural  state,  and 
near  where  it  is  mined,  to  obtain  the  best  results.  It 
will  be  noticed  in  examining  the  annexed  tables  that  it 
contains  a  large  per  cent,  of  volatile  matter  and  water. 
It  may  be  deprived  of  this  water  by  heating  the  lignite 
above  the  boiling  point  of  water,  but  if  a  piece  so  heated 
is  afterwards  allowed  to  remain  in  the  open  air  it  will 
again  absorb  from  the  atmosphere  the  same  quantity  of 
water  as  that  driven  off  by  the  heat. 

It  is  non-caking  in  the  fire,  and  yields  but  a  mod- 
erate heat,  that  is,  its  heating  power  in  general  is  below 
that  of  ordinary  bituminous  coals. 

The  number  of  units  of  heat  in  lignite  of  different 
qualities  and  from  different  parts  of  the  world  are 
given  in  the  tables,  and  its  relative  heating  power  may 
be  easily  determined  as  compared  with  coal  of  a  known 
calorific  value.  It  must  not  be  forgotten  in  making  use 
of  the  figures  in  the  columns  of  units  of  heat  in  these 
tables,  that  it  is  the  theoretical  numbers  which  are  given 
after  the  water  in  the  specimen  had  been  expelled  by 
heat,  the  quantity  of  heat  so  expended  in  its  evapora- 
tion does  imt  appear  in  the  calculation. 


44  COMBUSTION   OF    COAL. 

Lignite  contains  from  ten  to  twenty  per  cent,  of 
water,  which  must  be  evaporated  in  the  fire  before  any 
useful  effect  is  obtained,  and,  at  a  considerable  loss,  so 
this  must  be  taken  into  account  in  any  comparison 
made  with  other  fuels. 

The  use  of  lignite  in  this  country  is  so  limited  that 
it  has  at  present  little  or  no  commercial  value  except  in 
the  immediate  vicinity  where  it  is  mined ;  but  as  the 
vast  territories  west  of  the  Mississippi  are  developed  it 
will  then  become  a  matter  of  growing  importance,  as 
lignite  must  become  their  chief  fuel,  after  the  disap- 
pearance of  the  forests.  Very  extensive  deposits  occur 
in  California,  Colorado,  Nevada,  Utah,  Wyoming,  New 
Mexico,  Oregon  and  Alaska. 

Kentucky — Lignite  from  the  bluff  of  Fort  Jefferson, 
Ballard  county,  Kentucky. 

PROXIMATE  ANALYSIS  BY  PROFESSOR  E.  T.  COX. 

Specific  gravity 1.201 

PER  CENT. 

Fixed  carbon 40. 

Volatile  combustible  matter 23. 

Water 30. 

Ash,  reddish  yellow  or  flesh  tint 7. 

100. 

Total  volatile  matter 53.  per  cent. 

Coke,  reduced  in  bulk  and  nearly  the 

same  shape  as  the  original  specimen     47.  per  cent. 

100. 
Some  of  this  lignite  has  very  much  the  appearance 
of  coal;    hence,  it  is  apt  to  be  mistaken  for  it;  but  it 


LIGNITE.  40 

is  of  much  more  recent  date  than  true  coal,  and  has 
heen  formed  under  entirely  different  circumstances,  and 
derived  from  a  very  different  vegetation  than  that  which 
flourished  during  the  carboniferous  era. 

Washington  Territory — A  sample  of  Billingham  Bay 
coal,  Washington  Territory,  was  sent  by  Dr.  John  Evans 
to  Professor  E.  T.  Cox,  who  made  both  proximate  and 
ultimate  analyses  of  it,  with  results  as  given  below : 

PROXIMATE  ANALYSIS. 

PER  CENT. 

Fixed  carbon 58.25 

Volatile  combustible  matter 31.75 

Water 7.00 

Ashes,  reddish  brown 3.00 

100.00 

Coke 61.25  per  cent. 

Volatile  matter 38.75  per  cent. 

The  coke  slightly  shrunken,  dull  black. 

This  is  to  be  regarded  as  lignite  rather  than  a  true 
coal;  it  maybe  handled  without  much  loss,  has  a  bedded 
structure;  layers  about  one-eighth  inch  thick,  sometimes 
defined  by  a  thin  scale  of  carbonate  of  lime.  Color, 
glossy  black:  fracture,  slaty  and  parallel  to  stratification, 
in  the  opposite  direction  the  fracture  is  irregular  and 
brittle.  This  formation  has  much  less  earthy  matter 
than  mosi  tertiary  coals  or  lignites,  and  much  more 
carbon. 

ULTIMATE  ANALYSIS 

FIRST   SAMPLE.  PERCENT. 

Carbon 68.454 

Hydrogen 6.666 

Sulphur 1.000 


46  COMBUSTION    OF    COAL. 

Water  (at  212°) 7.000 

Ashes 3.400 

Oxygen,  nitrogen  and  loss 13.480 

100.000 

SECOND   SAMPLE.  PER  CENT. 

Carbon 67.090 

Hydrogen 4.555 

Sulphur 1.000 

Water  (at  212°) 7.000 

Ashes 3.100 

Oxygen,  nitrogen  and  loss 17.355 

100.000 
This  coal  (or  lignite)  contains  a  large  amount  of 
oxygen  and  is  deficient  in  the  amount  of  hydro-carbons, 
and  therefore,  more  difficult  of  ignition  than  most  of 
the  western  bituminous  coals,  but  it  is  rich  in  fixed  car- 
bon in  the  coke  and  will  therefore  be  a  durable  coal. 
It  is  intermediate  in  composition  of  its  ultimate  elements 
to  cannel  coal  and  lignites. 

Vancoover's  Island — Lignite,  color,  dull  black,  sub- 
metallic;  fracture,  foliated  and  slaty,  numerous  partings 
filled  with  scales  of  carbonate  of  lime. 

PROXIMATE  ANALYSIS  BY  PROFESSOR  E.  T.  COX. 

PER  CENT. 

Fixed  carbon 62. 

Volatile  combustible  matter 31. 

Water 4. 

Ash,  reddish  brown 3. 

100. 

Coke T 65  per  cent. 

Volatile  matter 35  per  cent. 


LIGNITE.  47 

This  lignite  shrinks  slightly  in  coking,  and  is  dull 
black  in  color. 

Colorado — Lignite  from  Carbon  City  on  the  Union 
Pacific  Railroad.     Specimen  brought  by  Edward  King. 

ANALYSIS  BY  PROFESSOR  E.  T.  COX. 

Color,  jet  black — specific  gravity 1.271 

Weight,  one  cubic  foot 80.68  lbs. 

PER  CENT. 

Fixed  carbon 41.25 

Volatile  combustible  matter 46.00 

Water 3.50 

A-li.  load  color 9.25 

100.00 

Coke 50.50  per  cent. 

Volatile  matter 49.50  per  cent.     • 

Coke — shrivelled,  cracked,  lusterless. 

Colorado — Lignite  from  Canon  City,  about  two  hun- 
dred miles  south  of  Denver  City. 

PROXIMATE  ANALYSIS  BY  PROFESSOR  E.  T.  COX. 

Color,  jet  black — specific  gravity 1.279 

Weight,  one  cubic  foot 79.23  lbs. 

PER  CENT. 

Fixed  carbon 56.80 

Volatile  combustible  matter 34.20 

Water 4.50 

A-li    urine  yellow 4.50 

100.00 

Coke 61.30  per  cent. 

Volai  ile  matter 38.70  per  cent. 

<"(,k. Lightly  swollen,  unchanged,  semi-lustrous. 

This  is  a  good  fuel. 


48  COMBUSTION    OF    COAL. 

Arkansas — Lignite  from  Ouachita  conntv.  This  lio-- 
nite  has  a  rather  rhomboidal  cleavage;  can  he  cut  with 
a  knife,  and  receives  a  good  polish,  which  gives  it  a 
much  blacker  appearance.  It  is  solid,  heavy,  compact, 
of  a  bluish-brown  color,  disintegrating,  however,  by 
exposure  to  the  atmosphere. 

PROXIMATE  ANALYSIS  BY  PROFESSOR  E.  T.  COX. 

PER  CENT. 

Fixed  carbon 34.50 

Volatile  combustible  matter 28.50 

Water  (at  260°) 32.00 

Ashes 5.00 

100.00 

Coke 39.5  per  cent. 

Volatile  matter 60.5  per  cent. 

This  lignite  was  distilled  in  a  small  iron  crucible,  to 
which  a  glass  receiver  was  attached  and  kept  cool  with 
water.  The  first  product  that  came  over  was  gas  hav- 
ing a  feeble  odor  of  sulphurous  acid  and  burning  with  a 
tolerably  bright  name.  The  gas  was  soon  accompanied 
by  ammoniacal  water,  a  yellowish  oil,  and  a  waxy  pro- 
duct ;  the  latter  rising  into  the  exit  pipe  of  the  glass 
receiver  whenever  the  fire  was  a  little  too  strong,  which 
proves  it  to  be  very  volatile;  but  when  condensed,  it  has 
the  consistency  of  lard,  and  the  color  of  beeswax.  The 
last  products  which  came  over  were  lubricating  oil  and 
paraffin  e. 

Three  thousand  seven  hundred  grains  of  this  lignite 
gave: 


LIGNITE.  4!> 

GRAINS.         PER  CENT. 

Coke 1,400  37.83 

Watery  solution,  containing  sulphurous 

acid,  organic  acids,  and  ammonia....  1,270  34.32 

Crude  oil 450  12.16 

Gas  and  lo<- 580  1;">.69 

3,700     100.00 

From  this  analysis  two  thousand  pounds  of  lignite* 
would  yield  35.40  gallons  crude  oil. 

Occasionally  small  segregations  are  found  in  the' 
lignite,  approaching  amber  and  retin-asphaltum ;  in 
fact,  much  of  the  coal  has  a  retin-asphaltum  aspect. 

Kentucky — Brown  coal  (lignite?),  sample  from  one 
and  a-half  miles  north-west  of  Blandville,  Ballard 
county. 

PROXIMATE  ANALYSIS  BY  PROFESSOR  E.  T.  COX. 
Specific  gravity.  1.173. 

PER  CENT. 

Fix ed  carbon 3 1  .< • 

Volatile  combustible  matter 48.0 

Water 1  1.5 

Ash,  white 9.5 

100.00 

Coke 40..')  per  cent. 

Volatile  matter 59.5  per  cent. 

This  coal  contains  from  twenty  to  thirty  per  cent, 
less  fixed  carbon  than  the  coals  of  the  carboniferous 
epoch,  and  usually  a  much  larger  quantity  of  hygro- 
oietric  moisture,  which  renders  them  inferior  as  fuel 
and  still  Less  applicable  for  the  generation  of  steam,  ami 
manufacturing  purposes  generallv. 
(5) 


50  COMBUSTION    OF    COAL. 

A  specimen  from  Robertson  county,  Texas,  taken 
from  a  seam  ten  feet  thick,  was  analyzed,  and  is  described 
by  Professor  E.  T.  Cox  (4),  as  a  lusterless,  dull  brown 
coal  with  irregular  fracture  and  much  inclined  to  shrink, 
crack  and  fall  to  pieces  on  exposure  to  the  air.  It  con- 
tained by  proximate  analysis, 

PER  CENT. 

Fixed  carbon 45.00 

G.as 39.50 

Water... 11.00 

Ash,  white 4.50 

100.00 

Coke 49.50  per  cent. 

Volatile  matter 50.50  percent. 

Heat  units 13,068 

Specific  gravity 1.232 

Weight  of  one  cubic  foot 77  lbs. 

Coke — slightly  shrunken,  lusterless,  and  bears  a  close 
resemblance  to  wood  charcoal. 


LIGNITE. 


51 


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COMBUSTION    OF    COAL. 


CLASSIFICATION  OK  COAL. 

Coals  are  classified  according  to  the  amount  of  car- 
bon and  volatile  matter  present  in  their  composition: 
the  following-  is  the  classification  adopted  by  Professor 
II.  D.  Rogers,  in  the  "Geology  of  Pennsylvania": 


Anthracites. 


Common 
Bituminous 
Coal 


Bituminous 
coal 


Hydrogenous  or  <r;\-  coals 


|  Hard  Anthracites. 

i  Semi  or  Gaseous  Anthracites. 

Semi-bitumin-    J  Semi-bituminous  cherry  coal,  and 
ous  coals 1  Semi-bituminous  splint  coal. 

[  Caking  coal. 

|   Cherry  coal. 

I   Splint  coal. 

f  Cannel  coals.  [hill,  etc.) 

|   Hydrogenous  Shaly  coal  (Torbane- 

[  Asphaltic  coal  (Albert  Mine.) 

Bituminous  Coal — When  coal  contains  as  much  as 
eighteen  or  twenty  per  cent,  of  volatile  combustible 
matter  it  is  called  bituminous.  The  passage  of  lignite 
into  bituminous  coal  is  as  gradual  as  that  of  bituminous 
coal  into  anthracite,  so  there  is  no  precise  line  of 
demarkation  between  these  classes  of  coal.  Some  bitu- 
minous coals  yield  upon  analysis  as  much  and  occa- 
sionally more  than  fifty  per  cent,  of  volatile  matter.  It 
may  be  said,  however,  to  range  from  twenty  to  fifty  per 
cent.,  and  will  hardly  admit  of  averaging,  as  scarcely 
any  two  mines  yield  coal  of  the  same  quality.  The 
amount  of  volatile  matter  in  bituminous  coal  can  not 
be  judged  from  its  appearance  simply,  and  perhaps  the 
easiest  and  best  way  to  arrive  at  it,  and  to  determine 


BITUMINOUS    COAL. 


53 


the  amount  of  fixed  carbon  at  the  same  time,  is  by 
proximate  analysis. 

The  use  of  the  word  bituminous  is  somewhat  mis- 
leading: there  is  no  bituminous  coal  in  this  country, 
which  contains  any  bitumen  in  its  composition.  In 
general,  this  word  is  applied  to  such  coals  as  have  a 
large  proportion  of  organic  elements  in  addition  to  its 
fixed  carbon,  and  includes  all  the  hydro-carbons,  water 
and  nitrogen,  in  its  composition. 

The  true  bitumens  are  destitute  of  organic  structure; 
they  appear  to  have  arisen  from  coal  or  lignite  by  the 
action  of  subterranean  heat,  and  very  closely  resemble 
some  of  the  products  yielded  by  the  destructive  distilla- 
tion of  those  bodies.  They  are  very  numerous,  and 
have  yet  been  but  imperfectly  studied. 

It  is  possible  that  its  name  has  been  applied  to  coal 
on  account  of  a  similarity  between  the  burning  of  a 
coal  rich  in  hydro-carbon  and  bitumen.  The  latter  is 
wry  inflammable,  and  burns  with  a  red,  smoky  flame. 

Professor  Rogers,  in  his  Geology  of  Pennsylvania, 
makes  a  distinction  between  what  he  calls  common  bitu- 
minous coals  and  hydrogenous  ^v  gas  coals.  His  scheme 
of  classification  will  be  found  on  page  .">:!.  It  is  scarcely 
possible  to  give  in  a  single  description  the  physical  prop- 
erties of  bituminous  coal,  which  will  be  applicable  to  all 
varieties. 

In  external  properties,  (23)  the  common  bituminous 
coals  range  in  color  from  a  pitch  black  to  a  dark  brown : 
their  luster  is  vitreous,  resinous,  or,  in  the  more  fibrous 
varieties,  silky :  their  structure  is  compacl  or  cuboidal, 


54  COMBUSTION    OF    COAL. 

slaty,  columnar,  and  even  fibrous;  and  their  fracture, 
irrespective  of  structural  joints  and  cleavage,  is  con- 
choidal,  and  often  flat  and  rectangular,  and  sometimes 
fibrous.  It  is  distinctive  of  these  coals  to  burn  with 
more  or  less  of  yellow  bituminous  flame  and  smoke,  and 
to  emit,  when  burning,  a  bituminous  odor.  In  'proxi- 
mate composition — namely,  in  fixed  carbon  or  coke,  vola- 
tile matter  or  combustible  gases,  and  earthy  sediment- 
ary residue  or  ashes — they  may  be  regarded  as  ranging 
between  the  following  general  limits : 

Fixed  carbon from  52  to  84  per  cent. 

Volatile  matter from  12  to  48  per  cent. 

Earthy   matter from    2  to  20  per  cent. 

Sulphur from    1  to    3  per  cent. 

Dried  at  a  temperature  of  212°  Fahr.,  the  yield  of 
water  is  from  one  to  three  or  four  per  cent. 

The  proportion  of  earthy  matter  is  of  course  too 
variable  to  have  a  maximum  limit  affixed  to  it,  as  all  the 
kinds  of  coal  may,  by  impurities,  graduate  into  carbona- 
ceous shales. 

In  ultimate  composition,  the  coals  of  this  class  maybe 
recorded  as  ranging  approximately  nearly  thus — 

Carbon 75  to  80  per  cent. 

Hydrogen 5  to    6  per  cent. 

Nitrogen 1  to    2  per  cent. 

Oxygen 4  to  10  per  cent. 

Sulphur 0.4  to  3  per  cent. 

Ash 3  to  10  percent. 


BITUMINOUS    COAL.  55 


Composition  of  Various  Bituminous  Coals. 
illinois. 
Smith's,  Warren  county.     Dr.  Norwood. 

PER  CENT. 

Fixed  carbon 51.7 

Volatile  matter 43.1 

Earthy  matter 5.2 

100.0 

Ashes,  red. 

Specific  gravity.  1.24. 

Montauk  Coal — A  compact,  deep  black,  caking  coal, 
laminae  very  indistinct,  breaks  into  irregular  cubes,  and 
contains  sonic  pyrites.     E.  T.  Cox. 

PER   CENT. 

Fixed  carbon 48.00 

Gas  35.00 

Water 11.50 

AAi.  brown 5.50 

100.00 

Coke 53.50 

Beat,  units 12,760 

Specific  gravity 1.232 

Weight  of  one  cubic  foot 77  lbs. 

Coke:   puffed,  lusterless,  amorphous. 

Bureau  county,  Illinois.     Dr.  V".  Z.  Blandy. 

PBE  TEN  I. 

Fixed  carbon 57.6 

Volatile  matter 28.8 

Moisture 11.2 

Ash,  nearly  white 2.4 

100.0 
i  ■,,)<, — ( [lose,  not  swollen. 

Specific  gravity,  1.316. 

Weight  oi  a  cubicfoot 80  lbs. 


56  COMBUSTION    OF    COAL. 


The  heat  units  in  this  coal,  determined  as  below,  are 

Carbon 576X14,54-4=      8,377 

Volatile  matter 288X20,115=     5,793 

Less 288  X    3,600=     1,037     4,756 


Total  heat  units 13,133 

Mercer  county,  Illinois.     Dr.  V.  Z.  Blandy. 


Fixed  carbon.... 
Volatile  matter. 

Moisture 

Ash,  fawn  color. 


PER  CENT. 

54.8 

31.2 

8.4 

5.6 

100.0 
Coke — pulverulent  between  the  fingers. 

Specific  gravity,  1.259. 

Weight  of  a  cubic  foot 78.49  lbs. 

Heat  units 13,123 

INDIANA. 

McClellan  and  Zellers'  Coal,  north  of  Brazil,  Chn 
county.  This  is  a  typical  block  coal,  a  dull,  lusterless 
black,  in  thin  lamina?,  separated  by  fibrous  charcoal 
partings,  very  strong  across  the  bedding  lines,  free  from 
pyrites  and  calcite,  and  is  highly  esteemed,  for  blast  and 
puddling  furnace  use.  The  specimen  analyzed  was 
fresh  from  the  mine  and  held  a  large  excess  of  water 
which,  on  exposure  to  the  air  of  the  laboratory  for  a 
few  weeks,  would  reduce  to  about  3.5  per  cent.  E.  T. 
Cox. 

PER  CENT. 

Fixed  carbon 56.50 

Gas 32.50 

Water 8.50 


BITUMINOUS    COAL.  57 


Ash,  white 2.50 

100.00 

Coke 59.00 

Heat  units,  wet  coal 13,588 

Heat  units,  dry  coal 14,400 

Specific  gravity 1.285 

Weight  of  one  cubic  foot 80.31  lbs. 

Cok( — laminate,  not  swollen,  lusterless. 

INDIANA. 

JElias  Cooprider's  Coal,  near  Middletown,  Clay  county. 
This  is  a  compact,  jet-black,  slightly  laminate,  caking 
coal,  with  some  evidence  of  pyrites  in  the  lower  part. 
E.  T.  Cox. 

TOP.  MIDDLE.  BOTTOM. 

Fix. m1  carbon..' 44.00  45.00  50.50 

(las 47.50  44.00  42.50 

Water 4.00  2.50  3.00 

Asli pink    4.50     brown   8.50   yellow    4.00 

Coke,  per  cent 48.50  53.50  54.50 

Heat  units 14.263  13,811  14,364 

Specific  gravity L.280  L.533  1.211 

Weight  of  one  cubic  foot 80.00  95.81  75.68 

Coke:     Vitreous,  puffed,  amorphous. 

PENNSYLVANIA. 

Conncllsville  Coal,  Fayette  county.  From  this  coal 
the  celebrated  foundry  coke  is  made.  The  specimen 
received  would  measure  about  one-half  a  cubic  foot; 
every  pari  of  it  displayed  prismatic  colors;  it  had  a  col- 
umnar structure,  inclined  to  be  granular,  and  easily 
broken  into  small  fragments.      E.  T.  Cox. 

I'll:  CENT. 

Fixed  carbon •..    65.00 

Gas 24.00 


58  COMBUSTION    OF    COAL. 

Water 4.50 

Ash,  white 6.50 


100.00 

Coke •. 71.50 

Specific  gravity 1 . 28 

Weight  of  one  cubic  foot 80.00 

Coke:     Of   steel    gray  color,    columnar,    very  strong, 
dense,  slightly  puffed  on  the  surface. 

The  heat  units  in  this  coal  are  : 

PER    CENT. 

Carbon 05X14,544=      9,454 

Volatile  matter 24X20,115  =    4,828 

Less 24><   3,600=       864   3,964 


Total  heat  units  13,418 

Youghiogheny    Coal,  Pennsylvania.     Geological    sur- 
vey of  Kentucky.     Professor  Peter. 

PER  CENT. 

Fixed  carbon 58.40 

Volatile  combustible  matter 35.00 

Moisture 1.00 

Ashes 5.60 


100.00 
The  heat  units  in  this  coal  are : 

Carbon 584X14,544=     8,494 

Volatile  matter 35X20,115=    7,040     

Less 35X   3,600=    1,260    5,780 


Total  heat  units 14,274 

This  is  considered  a  very  superior  gas  coal,  and  fur- 
nishes a  quality  of  coke  highly  valued  for  domestic  use. 

PENNSYLVANIA. 

Stone's  Gas  Coal,  Fayette  county.     This  coal  is  in 
common  use  in  many  cities  in  the  western  states  for  the 


BITUMINOUS    COAL.  59 


manufacture  of  illuminating  gas.  The  specimen  analyzed 
was  obtained  at  the  Indianapolis  gas  works,  and  said,  by 
the  superintendent,  to  be  first-class.     E.  T.  Cox. 

PER  CENT. 

Fi  xed  carbon 58 

Gas 34 

Water 3 

Ash,  white 5 

100 

Coke 63  per  cent. 

Heat  units 14,049 

.Specific  gravity 1.292 

Weight  of  one  cubic  foot 80.75  U>s. 

Coke:    slightly   puffed,   amorphous,  lusterless,  and  is 
much  esteemed  as  a  grate  and  stove  fuel. 

KENTUCKY, 

Coal  from  Sardric  and  Mud  river,  Mecklenburg 
county.  This  is  a  dull  black,  vitreous,  caking  coal,  with 
irregular,  resinous  fracture,  1  ami  me  indistinct,  no  visible 
pyrites.     E.  T.  Cox. 

SARDRIC.  MUD   RTVEE. 

Fixed  carbon 51.00  57.00 

Gas 42.50  37.00 

Water 2.00  3.50 

Ash,  white 4.50  2.50 

Coke 55.5(1  59.50 

Heal  units 14.43C.  14.4(H) 

Specific  gravity 1.325  L.280 

Weight  of  one  cubic  foot s-J.si  Lbs.  80.00  lbs. 

Coke:     Puffed,  lusterless,  amorphous. 

OHIO. 

Coal  from  NelsonviUe — From  the  Geological  Report, 

is.;:.. 


60 


COMBUSTION    OF    COAL. 


ANALYSIS  BY  PROF.  T.  G.  WOBMLEY. 


PORTION  OF  THE  SEAM. 


Specific  gravity , 


Water 

Volatile  matter. 
Fixed  carbon.... 
Ash 


Total. 


Sulphur 

Color  of  ash 

Nature  of  the  coke. 


Cubic  feet  of  permanent  gas  per  pound 
of  coal  


1.285 


6.20 
31.30 
59.80 

2.70 


100.00 


0.97 

Gray 

Compact. 

3.56 


1.272 


6.65 
33.05 
58.40 

1.90 

100.00 

0.41 

Yellow. 

Compact. 

3.24 


1.284 


5.00 

32.80 

53.15 

9.05 

100.C0 


0.94 

Gray. 

Compact. 

4.95 


An  average  of  the  above  three  samples  gives, 

Volatile  matter 3238  pe  r  cent. 

Fixed  carbon 5712  per  cent. 

Then,  taking  14,544  as  the  heat  units  in  carbon  (as 
has  been  done  in  the  preceding  examples),  and  20,115  as 
the  heat  units  of  the  combustion  of  the  combined  vola- 
tile matter,  deducting  3,600  units  for  the  heat  expended 
in  their  expulsion,  we  have, 

Carbon 5712X14,544=     8,308 

Volatile  matter 3238X20,115=     6,513 

Less 3238X  3,600=     1,166     5,347 


Total  heat  units  in  one  pound  of  coal 13,655 


GAS    COAL.  Gl 


CLASSIFICATION  OF  BITUMINOUS  COALS. 

It  will  serve  our  present  purpose  if  we  divide  all 
bituminous  coals  into  two  classes: 

CAKING  AND   NON-CAKING. 

Caking  coal  is  the  name  given  to  any  coal  which  when 
heated  the  lumps  seem  to  fuse  together,  and  swell  in  size, 
having  a  pasty  appearance  and  emitting  a  gummy  or 
sticky  substance  over  the  surface,  liberating  small 
streams  of  gas  which  appear  to  escape  from  a  considera- 
ble pressure  from  the  interior  of  the  coal,  and  which 
burn  with  a  bright  yellow  and  sometimes  a  reddish 
flame,  terminating  in  smoke.  A  characteristic  of  cak- 
ing coal  is  that  lumps,  either  large  or  small,  being  ren- 
dered pasty  by  the  action  of  the  heat,  will  cohere  in  the 
fire  and  form  a  spongy  looking  mass,  which,  not  unfre- 
quently,  covers  almost  the  whole  surface  of  the  grate. 
This  is  the  property  called  caking.  Caking  coals  rich 
in  hydn '-carbons  are  highly  esteemed  by  gas  manufac- 
turers. 

Gas  (,'oal — The  following  on  the  requisites  of  a  gas 
coal  is  from  the  pen  of  Mr.  .lames  McFarlane:     (18) 

"The  most  important  requisites  of  gas  coal  are,  first, 
that  it  contain  a  large  amount  of  volatile  combustible 
matter,  or  gas ;  second,  that  the  volatile  matter  be  of  a 
good  illuminating  power:  third,  that  the  coal  be  as  five 
as  possible  from  sulphur:  and  fourth,  that  the  coke  fur- 
nished by  tlir  carbonization  of  the  <'<>al  be  bulky,  and 
at  the  same  time  firm,  that  is.  pot  inclined  to  be  gran- 
ular. 


62  COMBUSTION    OF    COAL. 

"1.  The  percentage  of  the  volatile  matter  in  the 
coals  usually  employed  in  gas-making  is  from  twenty- 
five  to  forty,  and  in  cannel  coal  it  rises  to  sixty  or  sev- 
enty per  cent.,  a  portion  being  nitrogen  and  oxygen. 
A  ton  of  coal  should  produce  from  eight  thousand  to 
nine  thousand  feet  of  carbureted  hydrogen  or  illuminat- 
ing gas,  or  from  four  to  four  and  half  feet  per  pound,  the 
latter,  as  is  well  known,  being  the  product  of  a  fair  aver- 
age sample  of  Youghiogheny  coal.  Gas  works  practi- 
cally obtain  more  gas  per  pound  than  the  chemists  in  ana- 
lyzing the  coal,  doubtless  through  the  re-distillation  of 
tarry  matter  and  its  conversion  into  permanent  gas. 
Besides  this,  at  gas  works  the  measurement  is  taken  at 
a  high  temperature,  a  difference  of  five  degrees  chang- 
ing the  volume  of  gas  about  one  per  cent.  By  using 
the  steam -jet  exhaust  (a  recent  improvement)  an 
increased  quality  of  gas  is  obtained,  which  would  other- 
wise pass  off  in  little  bubbles  in  the  tar. 

"2.  That  the  gas  produced  from  the  coal  be  of  good 
illuminating  power  is  very  important.  The  standard  of 
gas  in  our  large  cities  ranges  from  fourteen  to  sixteen 
candle  power.  The  standard  candle  in  testing  gas  is  of 
spermaceti,  burning  at  the  rate  of  one  hundred  and 
twenty  grains  per  hour,  compared  with  a  standard  gas- 
burner  containing  live  cubic  feet  per  hour.  When  it  is 
supposed  to  give  fifteen  times  the  amount  of  light  fur- 
nished by  such  standard  candle,  the  gas  is  said  to  have 
fifteen-candle  power,  or  be  fifteen-candle  gas.  But  the 
standard  of  illuminating  power  can  easily  be  raised  by 
the  addition  of  a  few  per  cent,  of  some  rich  cannel  or 


GAS    COAL.  63 

oil  shale,  or  some  substance  of  the  character  of  albertite 
or  grahamite;  for  example,  from  a  coal  that  produces 
by  itself  fifteen-caudle  gas,  by  the  addition  of  ten  per 
cent,  of  cannel  the  gas  was  raised  to  the  standard  of 
eighteen  candles.  Many  coals  which  produce  gas  of  a 
low  illuminating  standard,  but  in  large  quantities,  and 
which  coke  well,  are  used  as  gas  coals. 

"3.  It  is  important  that  the  coal  should  contain  but 
a  small  proportion  of  sulphur  compound,  as  it  is  then 
easily  purified,  requiring  less  lime,  producing  a  better 
quality  of  gas,  and  the  coal  may  be  safely  stored  with- 
out danger  from  spontaneous  combustion.  Good  gas 
coal  should  not  require  more  than  one  bushel  of  lime 
to  purify  five  or  six  thousand  feet  of  gas.  The  sulphur 
in  coal  is  sometimes  in  combination  with  iron;  in  other 
cases  it  passes  off  in  a  volatile  state,  leaving  but  little  in 
the  coke.  For  gas-making  this  latter  is  a  disadvantage, 
as  the  less  sulphur  entering  the  gases  the  better,  since  it 
must  be  removed  by  purification.  For  the  blast  fur- 
nace, on  the  contrary,  the  less  sulphur  remaining  in  the 
coke  the  better,  since  it  is  the  sulphur  in  the  coke 
which  is  injurious,  and  not  that  in  the  hydrocarbons, 
which  pass  off  at  the  top  of  the  furnace  stack.  In  some 
cases,  however,  when  the  gas  carries  with  it  most  of  the 
sulphur,  the  gas  may  be  so  superior  in  illuminating 
power  as  to  warrant  its  use,  notwithstanding  its 
increased  cost  of  purification. 

"4.  A  ton  of  good  coal,  used  in  the  manufacture  of 
gas,  should  produce  thirty-five  to  forty  bushels  of  coke, 
weighing  thirty-five  pounds  to  the  bushel.     The  coke  is 


64  COMBUSTION   OF    COAL. 

used  for  heating  the  retorts,  and  should  burn  up  clean. 
with  hut  little  clinker.  There  should  he  a  surplus  of 
coke  when  a  large  amount  of  gas  is  manufactured, 
besides  that  used  in  the  gas-house,  and  this  is  valuable 
to  the  gas  manufacturer  as  a  merchantable  product, 
especially  in  localities  where  coal  of  a  good  quality  for 
domestic  and  other  purposes  is  expensive." 

Non-caking  Coals  have  the  property  of  burning  free 
in  the  fire  much  the  same  as  wood  charcoal  burns — that 
is,  heat  does  not  cause  them  to  fuse  or  run  together  in 
the  fire.  Perhaps  the  representative  non-caking  bitum- 
inous coal  is  the  block  coal  of  the  western  states,  and 
noticeably,  that  of  Indiana. 

Block  Coal — An  analysis  of  this  coal  is  given  on  page 
56  and  may  be  described  as  laminated  in  structure,- con- 
sisting of  successive  layers  of  coal  easily  separated  into 
thin  horizontal  slices  not  unlike  slate ;  between  these 
slices  of  coal  is  a  layer  of  fibrous  carbon  resembling 
charcoal.  In  appearance  it  has  a  dull  lusterless  face  on 
the  line  of  separation,  and  glistening  or  resinous  black 
when  broken  at  right  angles  to  its  horizontal  face.  A 
peculiarity  of  this  formation  and  that  which  gives  it  its 
name,  is  the  presence  of  fractures  occurring  in  the- coal 
bed  at  right  angles,  or  nearly  so,  and  extending  from  top 
to  bottom  of  the  seam,  enabling  the  miner  to  get  it  out 
in  rectangular  blocks  as  these  lines  of  fracture  indicate 
or  permit. 

It  is  a  very  strong  coal  and  will  burn  well  under  a 
heavy  load  without  crushing.    The  blocks  are  very  com- 


CARBONIZATION    OF    COAL.  65- 

pact  and  will  endure  rough  handling  and  stocking  with- 
out suffering  material  loss  from  abrasion.  This,  in  a 
commercial  point  of  view,  gives  the  block  coal  great 
value  over  and  above  its  other  good  qualities  as  a  fuel 
for  smelting  iron  and  generating  steam. 

Free-burning  coal  means  the  same  as  a  non-caking 
coal. 

CARBONIZATION  OF  COAL. 

Coke  is  the  residual  product  of  the  carbonization  of 
bituminous  coal.  The  only  coke  of  any  commercial 
value  is  that  made  from  caking  coals.  When  screen- 
ings and  small  particles,  as  well  as  ordinary  small  lumps 
of  such  coal,  arc  heated  sufficiently  high  and  protected 
from  the  atmosphere  (in- a  closed  vessel,  such  as  a  retort 
used  in  gas-making,  or,  coke  ovens,  when  manufactured 
on  a  large  scale),  the  volatile  portions  of  the  coal  are 
driven  oft',  and  a  coherent  mass  of  fixed  carbon,  con- 
taining usually  ffve  to  ten  per  cent,  of  earthy  matter, 
alone  remain;  this  is  called  coke. 

An  analysis  of  the  coal  from  which  the  celebrated 
Connellsville  coke  is  made  is  given  on  page  57.  This 
coke  is  very  hard,  occurs  in  long  pieces  not  unlike  ordi- 
nary stove  wood,  is  of  a  steel  grey  color,  having  a  bright 
metallic  luster.  It  is  used  largely  in  the  western  states 
for  the  melting  of  iron  in  cupola  furnaces,  etc.,  and  is  a 
most  excellent  fuel  for  such  purposes,  requiring,  how- 
ever,  a  strong  draft,  .judging  by  comparison,  about  the 
same  as  Lehigh  anthracite  coal  ;  it  yields  an  intense 
heat,  burn-  lice  under  a  strong  blast,  and  will  support  a 
(6) 


66  COMBUSTION    OF    COAL. 

considerable  weight  of  iron  above  it  in  the  cupola  with- 
out crushing. 

The  coke  remaining  after  the  distillation  of  coal  in 
retorts,  for  the  purpose  of  obtaining  an  illuminating 
gas,  is  known  as  gas  coke.  This  is  not  so  hard,  is  more 
easily  ignited,  and  burns  with  a  draft  less  intense  than 
the  preceding  coke.  This  is  a  favorite  fuel  for  domestic 
use,  and  burns  well  in  steam  boiler  furnaces,  or  in  any 
place  where  it  is  not  subjected  to  any  considerable 
pressure.  Its  power  of  resistance  seems  to  be  weakened 
by  the  manner  in  which  it  is  coked,  and  the  practice  of 
cooling  the  charges  drawn  from  the  retorts  by  turning  a 
stream  of  water  on  the  incandescent  coke  while  in  con- 
tact with  the  atmosphere;  but  aside  from  this,  the 
quality  of  coal  selected  for  gas-making  has  much  to 
do  with  it,  the  selection  being  made  with  reference  to 
the  quantity  of  gas  it  will  yield  rather  than  the  quantity 
and  quality  of  coke  remaining  after  distillation. 

THE  INFLUENCE  OF  TEMPERATURE   AND  PRESSURE  IN  THE  YIELD  OF 

COKE. 

Temjicrature — The  quality  of  coke  is  affected  by  the 
temperature  at  which  it  is  made.  In  no  case  can  coking 
occur  at  a  temperature  less  than  that  at  which  coal  suf- 
fers decomposition.  Coking  is  not.a  mere  fusing  of  coal 
into  a  mass;  it  is  rather  a  process  of  distillation,  in  which 
all  the  volatile  portions  of  the  coal  are  separated  from 
that  solid  portion  called  tixed  carbon.  This  distillation  can 
only  occur  at  a  high  temperature,  and  observation  shows 
that  as  a  general  rule  the  higher  the  temperature,  and 


COKE. 


67 


the  longer  the  exposure  to  that  temperature,  the  harder, 
more  dense,  and  less  easily  combustible  will  be  the  coke. 
M.  de  Marsilly  (20)  tried  the  effect  of  coking  during 
ninety-six,  and  one  hundred  and  twenty  hours,  and  found 
that  no  advantage  was  derived  by  prolonging  the  pro- 
cess beyond  forty-eight  hours. 

Pressure — In  order  to  test  the  effect  of  pressure  on 
the  quality  of  coke,  experiments  were  made  in  the  lab- 
oratory of  Professor  E.  T.  Cox,  during  which  he  was 
assisted  by  Dr.  G.  M.  Levctte.  The  following  table  gives 
the  results  of  the  experiments  as  determined  by  them : 
Table  X — Coals  Coked  uxder  Different  Degrees  of  Pressure. 


PLATINUM 
CRUCIBLE, 

IRON    R 

ETORT. 

NO. 

PROXIMATE 

NO 

3  INCHES 

G  INCHES 

12   INCHES 

ANALYSIS. 

MERCURY. 

MERCURY. 

MERCURY. 

MERCURY. 

1 

.".2.40 

59.10 

62.00 

62.80 

59.40 

2 

52.50 

54.35 

54.00 

54.30 

56.50 

3 

55.50 

56.10 

5G.40 

57.95 

56.15 

4 

57.50 

58.85 

60.40 

58.50 

5 'J.  25 

5 

58.50 

62.20 

01.75 

62.60 

63.40 

6 

57.90 

65.05 

65.00 

65.10 

66.10 

NAME  OF  THE  MINE  OR  OWNER. 

No.  1.  II.  K.  Wilson's,  Sullivan  county,  Indiana. 

No.  -.  Simpson's,  Knox  county,  Indiana. 

No.  3.  Shcpard  &  Haslett's,  Knox  county,  Indiana. 

No.  4.  Woodruff  k  Fletcher's,  Clay  county,  Indiana. 

No.  5.  Barnett's,  Clay  county,  Indiana. 

No.  G.  Stone's.  Pittsburg,  Pennsylvania. 


68  COMBUSTION    OF    COAL. 

iSTos.  1,  2,  3  and  6  of  the  table  are  caking  coals;  Nos. 
4  and  5  are  non-caking  or  block  coals. 

The  coke  from  Xo.  1  made  in  the  retort,  without 
pressure,  was  moderately  firm,  close  textured,  of  grayish 
black  color  and  without  luster;  with  a  pressure  exerted 
by  a  column  of  water  four  inches  high  (not  given  in 
the  table)  the  coke  was  not  increased  in  weight,  but 
appeared  more  compact  and  presented  a  radiated,  crys- 
talline structure,  the  rays  run  from  a  small  central  core 
to  the  circumference.  This  peculiar  structure  was  lost 
when  the  pressure  was  increased.  Up  to  a  six  inch  pres- 
sure of  mercury  there  was  a  gain  of  3.7  per  cent,  of 
coke,  which  was  very  dense  and  strong.  At  twelve 
inches  of  pressure  the  per  cent,  of  coke  was  scarcely 
more  than  that  obtained  without  pressure,  and  gave 
signs  of  puffing.  From  this  it  will  be  seen  that  six 
inches  of  mercury  gives  the  maximum  per  cent,  of  coke, 
and  that  beyond  this  the  heat  is  sufficient  to  liquify  the 
fixed  carbon,  and  expand  its  particles  so  as  to  make  a 
puffed,  porous  cake.  '  There  was  little  difference  in  the 
time  occupied  in  coking,  with  or  without  pressure. 
The  average  time  was  forty-five  minutes. 

Instead  of  the  coal  being  powdered,  as  was  the  case 
in  the  above  experiment,  some  pieces  a  little  larger  than 
a  pea  were  coked  under  six  and  twelve  inches  pressure, 
and  they  were  found  unchanged  in  shape  except  that 
the  edges  were  slightly  fused,  and  they  were  cemented 
together  like  a  pop-corn  ball.  The  color  and  appear- 
ance of  the  pieces  resembled  anthracite  coal  far  more 
than  coke.     Under  twelve  inches  pressure  the  pieces 


COKE.  69 

were  slightly  swollen,  but  in  color  and  structure  other- 
wise presented  the  same  appearance  as  the  former. 

Xos.  2  and  3,  caking  coals,  gave  a  cellular  coke  with- 
out pressure,  and  the  cells  were  only  slightly  enlarged 
by  twelve  inches  of  pressure.  The  weight  of  coke  in 
Xo.  2,  at  twelve  inches,  was  increased  by  four  per  cent., 
and  that  of  Xo.  3  by  only  0.G5  per  cent.,  while  under 
six  inches  pressure  the  increase  was  2.45  per  cent. 

Though  these  coals  do  not  puff  up,  under  pressure, 
as  much  as  Xos.  1  and  0,  the  result  clearly  points  out 
that  all  three  belong  to  a  class  of  coals  that  will  not 
make  a  good  coke  under  pressure,  but  that  the  coking 
oven,  like  the  retorts  at  the  gas  works,  should  be  sub- 
jected to  a  process  of  exhaustion. 

Xo.  4  coked  without  pressure,  and  gave  a  coke  that 
possessed  bat  little  cohesion;  as  the  pressure  increased 
the  coke  was  more  compact,  and  under  twelve  inches 
pressure  it  was  strong  and  good  ;  the  color,  like  that  of 
Xo.  1,  resembled  anthracite  rather  than  coke;  the  great- 
est increase  was  produced  by  pressure  of  twelve  inches, 
and  only  amounted  to  1.75  per  cent. 

Xo.  5.  This  is  one  of  the  dryest  burning  of  the  block 
coals  and  the  particles  were  but  slightly  coherent  even 
under  a  pressure  of  twelve  inches ;  t  he  increase  in  weight 
at  i  liis  pressure  amounted  to  4.9  per  cent. 

The  greatest  pressure  exerted  on  the  block  coals  did 
not  cause  the  carbon  to  become  Liquid  as  in  the  coking 
cals  and  the  [(article-  were  simply  cemented  together 
by  fusing  on  the   surface.     Lumps,  when    coked    under 


70  COMBUSTION   OF    COAL. 

pressure,  do  not  therefore  swell,  but  rather  become  more 
dense  and  homogeneous  with  an  increase  of  heat. 

Xo.  6.  The  effect  of  pressure  on  this  coal  was  quite 
different  from  that  of  Xo.  1,  and  equally  as  remarkable. 
The  weight  of  the  coke  continued  to  increase  up  to  a 
pressure  of  twelve  inches,  where  it  gained  8.2  per  cent. 
over  the  result  in  the  first  column,  but  it  was  puffed  up 
until  the  shape  resembled  a  hen's  egg  and  contained  a 
large  cavity  in  the  center  of  the  mass.  The  fracture 
presented  also  a  cellular  structure  like  a  sponge.  With- 
out any  pressure  this  coal  gave  a  moderately  dense  coke 
but  continued  to  puff  up  with  every  inch  of  pressure 
added. 

It  appears  that,  in  order  to  make  a  homogeneous 
good  coke,  the  fixed  carbon  of  the  coal  must  be  of  a  kind 
that  will  melt  at  the  lowest  possible  temperature,  for  if 
the  process  of  coking  produces  the  least  pressure  on  the 
volatile  hydrocarbons,  whereby  there  is  an  increase  of 
heat,  such  pressure  causes  so  complete  a  liquefaction  and 
expansion  of  the  fixed  carbon  that  the  coke  is  left  cellu- 
lar instead  of  being  compact.  If  such  a  coal  is  coked 
by  covering  it  with  an  inch  of  sand  and  leaving  the  cover 
of  the  retort  off,  the  coke  will  be  dense  and  strong  and 
without  cells  that  are  perceptible  to  the  eye.  On  the 
other  hand,  coals,  like  the  block  coal  of  Indiana,  which 
requires  a  very  high  temperature  to  meet  its  fixed  car- 
bon, does  not  have  its  fixed  coke  expanded  by  heat 
induced  by  an  over-pressure  of  the  eliminated  gas,  but 
as  far  as  tried  in  the  above  experiments,  the  solidity  of 
the  block  coal  coke  increased  as  the  pressure  was  aug- 


COKE.  71 

merited  by  raising  the  column  of  mercury  through  which 
the  gas  had  to  escape  ;  such  coals  then  are  eminently 
adapted,  in  the  raw  state,  for  smelting  iron  in  the  blast 
furnace. 

Mr.  A.  L.  Steavenson  read  a  paper  before  the  Iron 
and  Steel  Institute,  at  Newcastle,  England,  on  the  man- 
ufacture of  coke,  in  which  he  gives  some  interesting 
data  in  regard  to  coking  coal.  After  giving  a  descrip- 
tion of  the  furnaces  employed  in  the  particular  manu- 
factories to  which  he  refers  in  the  first  part  of  his  paper, 
he  then  goes  on  to  say:  "Two  hundred  and  thirty  tons 
<>f  coal  of  the  following  approximate  composition, 

TONS. 

Oxygon 15.3 

Carbon 195.3 

Hydrogen 10.4 

Nitrogen 2.3 

Sulphur 1.4 

\-!i 5.3 

230.il 
Yield,  on    coking,  about   sixty   per  cent,  of  coke,   of  the 
following  approximate  composition: 

TONS.. 

Carbon 132.7 

Ash .").:; 

138.0 
"Therefore,  the  composition  and  weight  of  the  mate- 
rials lost  in  coking  ;irc 

loss. 

Carbon 62.fi 

Hydrogen L0.3 

Nitrogen 2.3 


lZ  COMBUSTION    OF    COAL. 

Sulphur 1.4 

Oxygen 15.3 

To  complete  the  combustion  of  these  into  ]S~,  CO.,  H2  O 
and  S02  are  required  1023.4  tons  of  air,  making  a  total 
weight  of  waste  gases  of  1115.4  tons,  of  which: 

790.3  tons  are  nitrogen. 
229.5  tons  are  carbonic  acid. 
92.8  tons  are  steam. 
2.8  tons  are  sulphurous  acid. 

Which,  at  a  temperature  of  fifteen  hundred  deg.  Fahr., 
will  occupy  a  space  of  one  hundred  and  twenty-three 
million  nine  hundred  and  ninety-nine  thousand  cubic 
feet;  and  since  the  coking  of  two  hundred  and  thirty 
tons  of  coal  occupies,  on  an  average,  eighty-four  hours, 
we  have  twenty-four  thousand  four  hundred  and  ninety- 
three  cubic  feet  per  minute,  or  four  thousand  and  five* 
cubic  feec  less  than  the  observed  quantity  as  above. 

"Next,  as  to  the  heat  commonly  wasted.  "We  have 
1115.4  tons  of  mixed  gases,  at  a  temperature  of  fifteen 
hundred  deg.  Fahr.,  which,  if  they  could  be  reduced  to 
the  temperature  of  the  atmosphere  (say  sixty  deg. 
Fahr.),  we  would  have  the  following  heating  value  in 
tons  of  II,  O  (water)  raised  one  deg.  Fahr. 

TEMPERATURE. 

TUNS.      DECS.   SP.  HEAT.   TONS  H2  O. 

X 790.3  X  1440  X  -244  =  277,680 

CO-.  229.5  X  1440  X  -216  =  71,384 

II.,  O  92.8  X  1440  X  -475  =  63,477 

SO, 2.8  X  1440  X  .155  =  625 

Tons  II   O  (water) 413,166 

*  This  four  thousand  and  five  cubic  feet  refers  to  some  experiments  at  the 
kilns.  B. 


CANNEL   COAL.  73 


AVhich  is  equivalent  to  evaporating  415  tons  of  water 
at  212°  Fahr.  But  owing  to  the  fact  that  the  tempera- 
ture of  the  gases  was  only  reduced  750°  Fahr.,  instead 
of  1,440°  Fahr.,  the  above  quantity  is  reduced  to  about 
one-half,  or  216.1  tons,  evaporated  in  eighty-four  hours, 
or  2.6  tons  in  one  hour.  This  was  tested  in  an  actual 
experiment  (on  the  two  boilers  supplied  with  the  gases 
from  fifty  ovens,  coking  the  230  tons  in  eighty-four 
hours),  the  quantity  evaporated  in  one  hour  being  2.4 
tons,  an  approximation  quite  as  close  as  can  be  expected. 
"The  total  theoretical  heat  actually  developed  in  the 
process  of  coking  at  the  above  rate  is  equivalent  to 
evaporating  17  tons  of  water  per  hour,  which  is  thus 
expended: 

TONS. 

Eeat  utilized  by  the  boilers 2.40 

Heal  escaping  in  chimney 2.-~>4 

Heat  Lost  in  radiation  from  ovens  and  flues 12.06 

17.00 

"Thus,  even  in  the  plan  described,  but  a  small  per- 
centage of  the  total  boat  generated  in  the  ovens  is  util- 
ized, although  if  this  was  carried  out  throughout  the 
district  of  South  Durham,  where  in  colliery  boilers  not 
more  than  6  lbs.  of  water,  on  the  average,  is  evaporated 
per  1  lb.  of  coals,  we  should  have  a  saving  of  1,085,869 
tons  of  coal  per  annum,  or  a  money  value  of  £271,467 
($1,313,900.28)/' 

I    \NM.l.  I  OAL. 

Cannel  Coal  is  a  variety  of  bituminous  coal  very  rich 
in  hydrogen.  From  the  amount  of  combustible  matter 
which  it  contains,  and  the  readiness  with  which  this  is 


74  COMBUSTION    OF    COAL. 

given  off  in  combustion,  accounts  for  the  name  given  it 
by  the  miners  as  cannel,  a  corruption  of  candle  coal. 
This  coal  kindles  readily,  and  burns  without  melting, 
emitting  a  bright  flame  like  that  of  a  candle.  When 
thrown  in  the  fire  the  piece  splits  up  into  fragments, 
producing  a  crackling  noise  which,  from  a  fancied 
resemblance,  has  also  received  the  name  of  parrot  coal. 
In  appearance  this  coal  differs  from  all  other  bitu- 
minous coals;  its  structure  is  more  nearly  homogeneous 
than  others,  being  a  compact  mass,  varying  from  brown 
to  black  in  color,  and  having  usually  a  dull  resinous 
luster.  When  broken  it  does  not  usually  preserve  any 
distinct  order  of  fracture,  and  is  liable  to  split  in  any 
direction.  On  account  of  its  being  excessively  rich  in 
hydro-carbons  it  is  highly  esteemed  as  a  gas-coal,  pref- 
erence being  given  to  those  coals  in  which  hydrogen 
bears  the  greatest  proportion  to  the  contained  oxygen. 

ANALYSIS  OF  VARIOUS  CANNEL  COALS. 

An  analysis  of  cannel  coal  from  near  Franklin,  Pa., 
by  Professor  W.  Ii.  Johnson,  gave, 

PER  CENT. 

Fixed  Carbon 40.13 

Volatile  matter 44.85 

Earthy  matter 15.02 

100.00 
Cannel    coal    from   Dorton's   Branch,    Cumberland 
river,  Ivy.     Coal :    close-textured,  concentric-structured, 
brilliant,  conchoidal.     By  Dr.  D.  D.  Owen. 

PER  CEST. 

Fixed  carbon 55.1 

Volatile  matter 42.9 


CANNEL   COAL.  75 


Earthy  matter - 

100.0 
Specific  gravity.  1.25. 
Ashes,  orange-colored. 

Breckenridge,  Ky\,  cannel  coal.     Proximate  analysis 
by  Dr.  Peters. 

PER  CENT. 

Carbon 32.00 

Volatile  matter 54.40 

Moisture 130 

Ash 12.30 

100.00 
This  coal,  by  elementary  analysis,  gave, 

PER  CENT. 

Carbon 68.128 

Hydrogen 6.489 

Nitrogen 2.274 

Oxygen  and  loss 5.833 

Sulphur 2.476 

Ash 14.800 

100.000 
Buckeye     Cannel    Coal    Company,    Davis    county.. 
Indiana.     By  Professor  E.  T.  Cox. 

PROXIMATE  ANALYSIS 

PER  CENT. 

Fixed  carbon 42.00 

Gas 48.50 

Hydroscopic  water 3.50 

Ash,  white 6.00 

100.00 
Coke-    is  laminated,  not  swollen,  ln.-t.rl.— . 
Specific  gravity,  L.229. 
<  Ine  cubic  foot  weighs 76.87  lbs. 


76  COMBUSTION    OF    COAL. 


ULTIMATE  ANALYSIS  OF  THE  SAME. 

PER  CENT. 

Carbon 71.10 

Hydrogen  6.06 

Oxygen , 12.74 

Nitrogen 145 

Sulphur  1.00 

Ash 7.65 

100.00 
The  heat  units  in  this  coal  are  thirteen  thousand  one 
hundred  and  thirty-one,  thus : 

.7110  carbon  X  14,544=  10,340  carbon  heat  units. 
.045  available  hydrogen  X  62,032  =  2,791  hydrogen  heat  unit.-. 
10,340  carbon  heat  units. 
2,791  hydrogen  heat  units. 

13,131  total  heat  units  in  the  coal. 

SEMI-BITUMINOUS  COAL. 

Semi-bituminous  Coal  is  not  so  hard,  and  contains 
more  volatile  matter  than  true  anthracite.  In  this,  as 
in  all  other  classification  of  coals,  its  limits  must  be 
somewhat  arbitrarily  fixed.  In  appearance  it  more 
closely  resembles  the  anthracite  than  the  bituminous 
coals,  differing  from  the  former:  in  fracture,  as  being 
less  conchoidal;  it  is  not  so  hard;  is  of  a  less  specific 
gravity;  and  when  thrown  upon  the  fire  it  kindles 
much  more  readily  and  burns  faster  than  anthracite. 
It  takes  high  rank  as  a  fuel;  although,  containing  less 
carbon  than  anthracite,  it  is  quite  as  desirable  on 
account  of  the  readiness  with  which  it  kindles,  and  the 
quantity  of  heat  it  is  capable  of  giving  off  when  burned 


SEMI-ANTHRACITE    COAL.  77 

in  steam  boiler  furnaces,  and  in  stoves  for  domestic  use. 
It  is  much  more  easily  regulated  in  burning  than  anthra- 
cite, and  is  almost  entirely  free  from  the  smoke  and  soot 
of  ordinary  bituminous  coal. 

Analysis  of  semi-bituminous  coal  from  Cumberland, 
Maryland.     By  Professor  W.  R.  Johnson. 

Specific  gravity.  1.41. 

PER  CENT. 

Fixed  carbon 68.44 

Volatile  matter 17.28 

Earthy  matter 13.98 

Sulphur .71 

100.41 

Blossburg,  Pennsylvania,  from  Geological  Survey  of 
Pennsylvania. 

Specific  gravity,  1.32. 

PER  CENT. 

Fixed  carbon 73.1 1 

Volatile  matter 15.27 

Mar  thy  matter 10.77 

Sulphur .85 


100.00 

The  heat  units  in  this  coal   determined  as  below  are 

thirteen  thousand  one  hundred  and  fifty-five: 

Carbon 7311X14.544         10,633 

Volatile  matter 1527X20,115        3,072 

Less 1527  X    3,600  550       2,522 

Total  heat  units 13,155 

Si  Ml- AVI  EEBACITE  GOAL. 

The  semi-anthracite  coals    are    restricted,    with    few 
exceptions,  to  those   coals  which  possess  on   an   averag< 


COMBUSTION    OF    COAL. 


from  seven  to  eight  per  cent,  of  volatile  combustible 
matter.  In  consequence  of  this  element,  part  of  which, 
at  least,  resides  probably  in  a  free  or  gaseous  state  in 
the  cells  or  clefts  of  the  coal,  this  variety  kindles  more 
promptly,  and,  when  sufficiently  supplied  with  air,  burns 
more  rapidly  than  the  hard  anthracite. 

Wilkesbarre,  Pennsylvania,  semi-anthracite,  de- 
scribed as  compact,  conchoidal,  iron-black,  splendant. 
Geological  survey  of  Pennsylvania. 

Specific  gravity,  1.40. 

PER  CENT. 

Fixed  carbon 88.90 

Volatile  matter 7.68 

Earthy  matter 3.49 

100.07 

Neglecting  the  .07  we  have  in  this  coal  14,199  units 

of  heat,  thus — 

Carbon 8890x14,544=     12,930 

Volatile  matter 0768X20,115=     1,545 

Less 0768  X    3,600=       276       1,269 


14,199 

ANTHRACITE  COAL. 

True  anthracite,  when  pure,  is  sIoav  to  ignite,  con- 
ducts heat  very  badly,  burns  at  a  very  high  tempera- 
ture, radiates  an  intense  warmth,  and  is  difficult  to 
quench.  Generating  almost  no  water  during  its  com- 
bustion, it  powerfully  dessicates  the  atmosphere  of  an 
apartment  in  which  it  is  burning. 

It  consists,  when  pure,  (23)  of 

Carbon from  90  to  94  per  cent. 

Hydrogen from    1  to    3  per  cent. 


ANTHRACITE    COAL.  7!' 


Oxygen  and  nitrogen .from    1  to    3  per  cent. 

Water from    1  to    2  per  cent. 

Ashes from    3  to    4  per  cent. 

The  constituents  which  vary  most  are,  of  course,  the 
carbon  and  earthy  matter. 

Hard  anthracite,  from  its  great  richness  in  carbon 
and  its  density,  stands  at  the  head  of  all  coals  for  its  heat 
generating  power,  if  adequately  supplied  with  air.  It  is 
the  most  economic  of  all  fuels — weight  for  weight — for 
smelting  and  melting  iron  and  the  other  metals. 

The  superior  density  of  hard  anthracite  over  every 
other  kind  of  coal,  by  lessening  the  room  demanded  for 
stowage,  gives  it  a  decided  preference  in  this  respect  as 
a  fuel  for  ocean  steamers. 

In  btirnins:  it  neither  softens  nor  swells,  and  does  not 
give  off  smoke;  the  name  is  quite  short,  and  has  a  yel- 
lowish tinge  when  first  thrown  upon  the  lire,  which 
soon  changes  to  a  faint  blue,  with  occasionally  a  red 
tinge,  'i  flame  being  quite  short  and  free  from  parti- 
i  solid  carbon,  has  the  appearance  of  being  trans- 

parent. 

When  broken  it  presents  a  conchoidal  appearance, 
and  appears  quite  homogeneous  in  structure.  It  will 
stand   weathering  and  stowage  better  than   other  coals. 


lysis  of  Anthracite  Coal  from  Tamaqua,  Penkstlvama. 
geological  survey  of  pennsylvania. 
This    coal    is    described    as    compact,    slaty,    con- 
choidal,  greyish  black,  splendant. 


80  COMBUSTION    OF    COAL. 


Specific  gravity,  1.57. 

PKR    CENT. 

Fixed  carbon 92.07 

Volatile  matter 5.03 

Earthv  matter 2.90 


KiO.OO 
Ashes,  white. 

Units  of  heat  in  1  pound  of  coal 14,221 

Beaver   Meadow    (Pa.)    Anthracite.      Prof.    W.    E. 
Johnson. 

Specific  gravity.  1.55 

PER  CENT. 

Fixed  carbon  90.20 

Volatile  matter 2.52 

Earthy  matter 6.13 

98.85 
No  explanation  is  given  by  Professor  Johnson  for 
the  1.15  per  cent,  loss  not  accounted  for  in  the  analysis, 
but  neglecting  this,  we  have  13,535  units  as  the  calorific 
power  of  this  coal,  determined  as  follows: 

Carbon 9020  X  14,544  = 13,119 

Volatile  matter 0252X20,115  =   507 

Less 0252X3600     =     91=       416 


Total  heat  units 13,535 


CHATTER    IV. 

ANALYSIS  OF  rnAL. 

Analysis,  Chemical,  Qualitative,  Quantitative,  Proximate — Selection* 
of  Samples  for  Analysis — Method  of  Conducting  a  Proximate- 
Analysis — Elementary  Analysis  —  Determination  of  Sulphur 
and  Phosphorus — Carbon  —  Hydrogen — ( lai'bureted  Hydrogen, 
— Sulphur — Products  obtained  from  Coal. 

Analysis — The  separation  of  a  body  into  its  constitu- 
ent elements  is  called  chemical  analysis;  when  it  is 
desired  to  know  simply  what  elements  compose  a  body 
it  is  known  as  qualitative  analysis:  when  the  quantity  of. 
each  element  is  to  be  determined  it  is  then  known  a> 
quantitative  analysis.  When,  as  in  the  ordinary  analysis 
of  coal,  it  is  desirable  to  determine  what  percentage  of 
volatile  matter,  lixed  carbon,  and  ash.  are  contained  in 
a  given  sample,  this  process  is  known  as  -proximate  anal- 
ysis, and  simply  informs  as  to  the  physical  peculiarities 
of  the  coal  and  not  as  to  its  elementary  composition. 

The  elementary  analysis  of  coal  shows  it  to  be  prin- 
cipally compos, .,l  of  the  following  simple  substances: 

<  larbon  ;  <  >xygen  ; 

Hydrogen;  Sulphur:  and 

Nitrogen;  Ash. 

Ash  is  not  a  simple  substance,  lmt  represents  the 
incombustible  matter  of  whatever  composition  remain- 
ing in  the  furnace  after  combustion. 

By   proximate  analysis  the  coal    would    be  said  to 

contain 
(7) 


82  COMBUSTION    OF    COAL. 

Fixed  carbon;  Moisture  or  water; 

Volatile  matter;  Ash. 

In  the  analysis  of  coal  it  is  desirable  to  know, 

1.  The  percentage  of  volatile  matter  it  contains. 

2.  The  percentage  of  fixed  carbon. 

3.  The  percentage  of  earthy  matter,  or  the  presence 
of  such  bodies  as  do  not  contribute  to  its  heating  value. 

This  can  only  be  arrived  at  by  a  process  of  destruc- 
tive distillation. 

Professor  E.  T.  Cox,  State  Geologist  of  Indiana,  has 
given  the  analysis  of  coals  particular  attention.  His 
suggestions  in  regard  to  samples,  and  his  method  of 
conducting  analysis,  whether  proximate  or  elementary, 
are  given  below;  also,  his  method  of  determining  the 
amount  of  sulphur,  phosphorus,  iron  and  alumina  in 
coal. 

SamjAes — It  is  a  matter  of  no  little  difficulty  to  select 
from  a  mine  a  proper  sample  for  analysis,  at  least  such 
a  sample  as  will  represent  the  average  commercial  value 
of  the  seam.  The  best  way,  therefore,  is  to  take  a 
sample  from  the  top,  middle  and  bottom  of  the  seam. 
These  should  be  carefully  labeled,  wrapped  in  paper  and 
sent  to  the  laboratory  as  soon  thereafter  as  practicable. 
On  arriving  at  the  laboratory  they  should  be  taken  in 
hand  at  once.  About  a  pound  of  each  sample  should 
be  pulverized  fine  enough  to  be  passed  through  a  porce- 
lain colander  with  one-tenth  inch  perforations;  then 
transferred  to  bottles  with  good  cork  stoppers.  Each 
bottle  should  be  labeled,  showing  the  date  of  mining, 
when  bottled,  name  of  mine,  etc.     These  bottles  serve 


PROXIMATE    ANALYSIS.  83 

as  stocks  from  which  the  different  quantities  are  to 
be  taken  that  serve  for  analysis.  It  is  not  a  good 
plan  to  mix  the  portions  taken  from  different  parts  of 
the  seam  and  consider  the  mixture  an  average  sample, 
so  that  one  set  of  analysis  may  serve  ;  for  though  it 
might  furnish  a  fair  statement  of  the  commercial  value 
of  the  seam,  it  would  leave  us  in  ignorance  of  much  use- 
ful information  in  regard  to  the  true  character  of  the 
seam. 

PROXIMATE  ANALYSIS. 

One  gram  is  charred  in  a  covered  platinum  crucible 
of  about  one  fluid  ounce  capacity.  The  heat  is  derived 
from  a  three-jet  Bunsen  gas  burner,  and  the  crucible  kept 
at  a  bright  red  heat  until  the  escaping  gas  ceases  to  burn 
and  the  condensed  carbon  disappears  from  the  cover 
The  weight  of  the  charred  mass  gives  the  coke,  and  the 
volatile  matter  is  estimated  by  the  loss.  To  determine 
the  hygroscopic  water,  one  decigram  of  pulverized  coal 
is  weighed  in  a  small,  shallow  platinum  capsule  and 
placed  in  a  hot-air  bath,  where  it  remains  at  a  tempera- 
ture of  100  to  105  cleg.  Cent,  for  one  hour;  the  loss  gives 
the  water.  The  capsule,  with  the  dry  coal,  is  then 
placed  over  a  strong  name  of  a  Bunsen  burner  until 
it  is  consumed  to  ash. 

The  weight  of  the  ash  is  deducted  from  the  coke  to 
find  the  fixed  carbon,  and  the  weight  of  the  water  is 
deducted  from  the  volatile  matter  to  find  the  per  cent. 
of  combustible  gas. 

All  this  appeal's  very  simple,  but  it  requires  great 
•  •are  and  attention  to  obtain  reliable  results.     The  tern- 


84  COMBUSTION    OF    COAL. 

perature  of  100°  C  (212  Fahr.)  is  recommended, 
since  it  is  believed  that  a  higher  temperature  is  no 
more  effective  and  is  more  liable  to  produce  decompo- 
sition   of  the  volatile  constituents. 

ELEMENTARY  ANALYSIS. 

The  combustion  is  best  performed  in  a  hard  glass 
tube,  twenty  inches  long  and  three-quarters  of  an  inch 
in  diameter. 

Twelve  inches  of  the  posterior  end  is  filled  with  a 
tightly-rolled  coil  of  fine  copper  gauze.  This  is  oxidized 
by  drawing  air  through  the  red-hot  tube  with  an  aspi- 
rator. The  usual  appliances  are  used  to  dry  the  oxygen 
and  free  it  from  carbonic  acid  and  other  impurities, 
and  also  arrest  the  hydrogen,  sulphur  and  carbonic  acid. 

Previous  to  commencing  the  combustion,  a  current 
of  pure  oxygen  is  passed  through  the  heated  tube  to 
complete  the  oxidation  of  the  copper  and  expel  the  last 
trace  of  moisture.  Two  decigrams  of  pulverized  coal 
are  now  placed  in  a  platinum  boat  and  inserted  in  the 
anterior  part  of  the  tube,  about  three  inches  from  the 
copper.  The  heat  of  the  gas  furnace  is  applied  with 
due  precaution,  and  the  combustion  is  completed  when 
the  coal  has  been  burnt  to  ash  and  oxygen  bubbles  pass 
freely  through  the  potash  apparatus.  When  the  hydro- 
gen, sulphur,  potash  apparatus  and  potash  U  tube  have 
been  weighed,  another  analysis  may  be  proceeded  with, 
and  in  this  way  as  many  as  four  combustions  may  be 
made  in  a  day.  A  good  tube  will  serve  for  ten  or 
twenty  combustions.     The  potash  apparatus  should  be 


ELEMENTARY    ANALYSIS. 


renewed  after  every  third  combustion,  in  order  to  insure 
a  proper  absorption  of  the  carbonic  acid. 

The  advantages  to  be  derived  from  this  mode  of 
conducting  the  analysis,  are:  You  are  enabled  to  watch 
the  combustion  of  the  coal  and  see  when  it  is  com- 
pleted; the  ash  may  be  determined  at  the  same  time 
and  the  tube  is  at  once  ready  for  the  reception  of 
another  sample  of  coal.  Xitrogen  is  determined  by 
Varrentrapp  and  Will's  method,  i.  e.,  by  conversion  into 
ammonia.  The  ammonia  is  received  in  a  measured 
quantity  of  standard  oxalic  acid,  and  the  amount  of 
free  acid  remaining  is  determined  by  neutralizing  with 
a  standard  solution  of  soda.  The  quantity  of  acid  sat- 
urated by  ammonia  is  then  found  from  the  difference. 

DETERMINATION  OF  SULPHUB  AND  PHOSPHORUS. 

There  is,  generally  speaking,  less  reliance  to  be 
placed  in  published  statements  of  the  amount  of  sul- 
phur and  phosphorus  in  coals  than  in  any  one  of  its 
other  elementary  constituents. 

The  results  are,  as  is  well  known,  generally  under 
rather  than  over  the  actual  amount  of  sulphur  presenl 
in  coal. 

The  loss  is  due  to  a  portion  of  the  sulphur  being 
converted  into  sulphureted  hydrogen  and  the  phos- 
phorus into  phosphureted  hydrogen,  which  escapes 
during  the  process  of  dissolving  the  coal.  In  order  to 
avoid  this  loss,  five  decigrams  of  coal  are  fused  with 
eighl  grains  of  caustic  potash  and  two  grains  nitrate  of 
potash,  in  a  silver  crucible. 


86  COMBUSTION    OF   COAL. 

Both  the  caustic  potash  and  nitrate  of  potash  should 
be  tested  for  sulphur  and  the  per  cent,  marked  upon  the 
bottle.  The  half  gram  of  powdered  coal  is  placed  in 
the  crucible  and  moistened  with  alcohol,  eight  grams  of 
potash  are  then  put  in  with  the  coal  and  placed  over  a 
moderate  heat  until  the  potash  is  melted,  after  which 
two  grams  nitrate  of  potash  are  added,  the  whole  is 
kept  at  a  gentle  heat  for  about  two  hours  or  until  all  the 
moisture  is  expelled;  the  heat  is  then  increased  until 
all  ebullition  ceases.  The  coal  should  dissolve  without 
deflagration  from  ignition.  After  cooling,  the  contents 
of  the  crucible  are  dissolved  out  with  water  and  neutral- 
ized with  hydrochloric  acid,  evaporated  to  dryness,  mois- 
tened with  hydrochloric  acid  and  re-dissolved  with 
water.  Filter  out  the  silicic  acid,  heat  the  filtrate  and 
precipitate  the  iron  and  alumina  with  ammonia  and 
determine  the  sulphuric  acid  in  the  filtrate  with  chloride 
of  barium. 

The  phosphoric  acid  is  precipitated  with  the  iron, 
and  to  separate  it,  the  precipitate  is  dissolved  from  the 
filter  with  a  weak  solution  of  hydrochloric  acid,  and 
then  evaporated  to  dryness  to  separate  the  last  trace  of 
silicic  acid. 

Moisten  with  nitric  acid,  dissolve  in  water,  filter  and 
precipitate  the  phosphoric  acid  with  molybdate  of 
ammonia.  "Wash  the  precipitate  as  directed  by  Fre- 
senius,  dissolve  with  ammonia  and  precipitate  phosphoric 
acid  with  sulphate  of  magnesia.  In  order  to  determine 
the  per  cent,  of  iron  and  alumina,  it  is  better  to  take 
another  half  gram  of  coal  and  fuse  as  before.     The  iron 


(ARBOX. 


87 


and  alumina  are  then  precipitated  from  the  hot  solution 
with  ammonia,  and  the  alumina  is  separated  by  digest- 
ing the  precipitate  with  hydrate  of  potash  in  a  silver 
crucible. 

This  mode  of  determining  the  sulphur,  phosphorus, 
iron  and  alumina  in  coal,  is  simple,  expeditious  and  accu- 
rate. It  has  been  adopted  after  repeated  trials  of  all 
other  known  processes,  and  leaves  nothing  to  he 
desired. 

CARBON  AND  HYDROGEN. 

Carbon — {Symbol  C;  atomic  weight  12).  This  is  one 
of  the  most  widely  diffused  and  abundant  of  the  ele- 
ments. It  exists  in  several  attotropic  states:  that  is,  it 
exists  in  several  conditions,  each  having  different  physi- 
cal properties,  whilst  its  chemical  properties  remain 
unchanged. 

The  commonest  forms  in  which  pure  carbon  occurs 
are  the  diamond,  black  lead  and  charcoal.  We  can 
scarcely  imagine  three  solids  more  unlike  in  their  phys- 
ical properties  than  these,  yet  chemically,  they  are  the 
same  thing:  that  is,  they  yield  upon  analysis  nothing 
hut  carbon.  It  is  the  principal  constituent  of  anthra- 
cite coal;  it  constitutes  about  one-half  of  bituminous 
coal:  and  is  an  essential  element  in  organic  bodies,  from 
which  it  may  he  separated  in  the  form  of  charcoal,  by 
distilling  oil"  the  more  volatile  elements. 

Carbon  unite-  directly  with  oxygen,  sulphur,  nitro- 
gen, ami  a  few  of  the  metals,  the  latter  at  high  temper- 
atures only.  The  two  direct  inorganic  compounds  of 
carbon  and  oxygen  are  known  as  carbonic  oxide  and 


88 


COMBUSTION    OF    COAL. 


carbonic  acid;  the  proportions  are  shown  in  the  follow 
ing  table: 


Table  XI. 

SYMBOL. 

COM  POSITION. 

by  weight: 

PERCENTAGE. 

CARBON. 

OXYGEN. 

TOTAL. 

CARBON. 

OXYGEN. 

TOTAL. 

Carbonic  Oxide. 
Carbonic  Acid.... 

C  0 

co2 

12 
12 

1G 

28 
44 

42.80 
27.27 

57.14 

72.73 

100 
100 

These  are  the  two  principal  gases  formed  in  the  fur- 
nace by  the  combustion  of  the  carbonaceous  portions  of 
the  fuel.  The  table  of  products  obtained  from  coal 
(page  94)  show  about  fifty  different  combinations  of 
carbon  with  different  elements  and  in  different  propor- 
tions. 

Almost  all  the  elementary  substances  of  which  the 
specific  heat  and  atomic  weight  are  known,  give,  when 
these  two  properties  are  multiplied  into  each  other,  a 
product  approximating  an  average  of  6.34.  Carbon  is 
•one  of  the  exceptions  to  this  rule,  as  the  following  will 
show : 

SPECIFIC         ATOMIC 

HEAT.        WEIGHT.      PRODUCTS. 

Carbon  (diamond) 0.1469         12  1.76 

Carbon  (graphite) 0.2008         12  2.41 

Carbon  (wood  charcoal) 0.2115         12  2.90 

The  other  two  exceptions  arc  boron  and  silicon. 
Carbon  is  quite  remarkable  for  the  differences  in  its 
physical  conditions,  and  this  is  sometimes  brought  for- 
ward as  a  partial  reason  for  the  low  product  shown  in 


HYDROGEN.  89 


the  above  table.  There  is  no  doubt  this  fact  has  much 
to  do  with  it,  but  is  not  a  very  satisfactory  way  of  dis- 
posing of  so  marked  a  difference  in  an  element  so 
widely  diffused,  and  so  generally  employed  in  manufac- 
tures and  domestic  use. 

Hydrogen — (symbol  II;  atomic  weight  1),  is  the  light- 
est substance  known.  When  pure  it  is  colorless,  taste- 
less, and  inodorous.  It  is  one  of  the  few  substances 
known  to  us  only  in  the  gaseous  state.  The  theory  that 
hydrogen  is  the  vapor  of  a  metal  was  proposed  by  the 
French  chemist,  Dumas,  about  forty-nine  years  ago 
(1830?),  but  from  our  knowledge  of  the  gas  we  can 
scarcely  imagine  it  to  be  solidified  except  by  the  with- 
drawal of  heat  until  no  more  can  be  extracted,  or,  until 
absolute  zero  (461  deg.  below  the  zero  of  Fahr.)  is 
reached,  when,  of  course,  hydrogen  would  cease  to  exist 
as  a  gas,  and  would  become  inert  or  assume  a  solid  state. 
and  would  bo  remain  until  a  rise  in  temperature  would 
permit  molecular  motion,  and  so  restore  it  to  its  gaseous 
form.  Many  experiments  have  been  made  to  reduce  it, 
if  possible,  to  a  liquid  state.  In  the  Scientific  American, 
February  23,  1878,  is  an  engraving  of  the  apparatus 
employed  by  M.  Cailletet, f>f  Paris,  in  his  experiments, 
during  which  he  succeeded  in  liquefying  hydrogen.  It 
is  said  that  M.  Raoul  Pictet  has  not  only  succeeded  in 
obtaining  liquefied  hydrogen,  but  also  Bolidified  it  at 
( l-eneva,  January  in.  1878. 

Hydrogen  is  no1  Pound  in  a  free  state,  though  it  is 
an  essential  elemenl  in  all  organic  substances,  from 
which   it    may   be    separated  by    a  process  of  destructive 


90  COMBUSTION    OF    COAL. 

distillation.  It  occurs  in  nature  in  combination  with 
carbon;  the  compound  which  contains  it  in  greatest 
abundance  is  marsh-gas,  of  which  hydrogen  forms  one- 
fourth,  the  formula  being  CH  u  This  same  gas  often 
occurs  in  mines,  where  it  is  known  as  lire-damp. 

Under  ordinary  temperatures  and  at  ordinary  press- 
ures hydrogen  has  no  tendency  to  enter  into  combina- 
tion with  other  substances.  It  combines  with  eight 
parts  of  oxygen  to  form  water,  but  this  combination 
does  not  take  place  spontaneously.  The  two  gases  will 
remain  together  as  a  mere  mechanical  mixture  any 
length  of  time;  upon  the  application  of  a  spark,  how- 
ever, the  chemical  union  of  the  two  gases  is  instanta- 
neous and  violent.  Liquid  water  contains  1238  times  its 
volume  of  free  gaseous  hydrogen,  and  when  we  con- 
sider the  oceans  of  water  throughout  the  world  and 
the  volume  of  hydrogen  required  to  form  this  water,  it 
makes  a  quantity  which,  expressed  by  ordinary  meas- 
urements, is  almost  beyond  comprehension. 

Pure  hydrogen  burns  in  the  atmosphere  with  a  pale 
blue  light,  scarcely  perceptible  in  full  daylight,  giving 
off  an  intense  heat.  Favre  and  Silberman  ascertained 
the  heat  of  one  pound  of  hydrogen  burned  in  oxygen  to 
be  sufficient  to  raise  the  temperature  of  62,032  pounds 
of  water  one  degree  Fahr.  This  is  no't  equalled  by  any 
other  known  substance. 

Carbureted  hydrogen  has  long  been  employed  as  an 
illuminating  agent,  and  has  been  obtained  by  the  distil- 
lation of  the  volatile  portions  of  bituminous  coal,  yield- 


HYDROGEN.  91 


ing  a  hydro-carbon  gas  of  the  following  approximate 
composition : 

Hydrogen 41.85 

Marsh-gas 39.11 

Carbonic  oxide 5.86 

defines 7.95 

Nitrogen 5.01 

Carbonic  acid .22 

100.00 

This  composition  will  vary,  of  course,  in  different 
sections  of  the  country,  owing  to  different  coals  employed, 
and  care  in  manufacture.  The  production  of  hydro- 
carbon gases  on  a  large  scale  for  illuminating  purposes 
lias  engaged  the  minds  of  inventors  not  only,  but  has 
profitably  employed  vast  sums  of  money  in  this  great 
and  almost  indispensable  industry.  Within  a  few  years 
past  the  possibility  of  economically  decomposing  water 
in  order  to  utilize  its  hydrogen  as  an  illuminating  agent 
has  been  fully  demonstrated  on  a  large  scale,  and  it 
appears  as  if,  in  addition  to  its  employment  as  an  illu- 
minating agent,  it,  at  no  very  distant  day,  by  virtue  of 
it-  extraordinary  and  unparalleled  heating  power,  is  des- 
tined  to  supercede  our  present  wasteful  method  of 
heating  city  homes,  mercantile  and  manufacturing  build- 
ings, etc.,  promising  at  once  a  heat  in  any  desired  quan- 
tity, easily  controlled,  with  perfect  cleanliness,  and 
more  economical  in  many  cases  than  crude  fuel. 

Hydrogen  unites  with  nitrogen  to  form  ammonia, 
the    formula   being   NIL. 


92  COMBUSTION    OF    COAL. 

Sulphur — (symbol  S;  atomic  weight  32),  is  often 
found  in  coal  in  combination  with  iron,  and  is  known 
as  iron  pyrites.  Some  specimens  are  of  great  beauty, 
but  underneath  this  attractive  exterior  lurks  a  danger- 
ous enemy  to  steam  boilers.  Sulphur  is  highly  inflam- 
mable, and  when  heated  in  the  air  to  a  temperature  of 
about  482°  Fahr.  it  takes  fire  and  burns  with  a  clear  blue, 
feebly  luminous  flame,  being  converted  into  sulphurous 
oxide,  SO,.  In  its  chemical  relations  sulphur  is  the  rep- 
resentative of  oxygen,  to  which  it  is  equivalent,  atom  to 
atom.  Oxygen  gas  and  sulphur  vapor  alike  support 
the  combustion  of  hydrogen,  charcoal,  phosphorus,  and 
the  metals  to  form  precisely  analogous  compounds. 

"The  presence  of  sulphur  in  common  coal  gas  has 
received  considerable  attention,  from  a  sanitary  point  of 
view,  by  gas  chemists,  who  are  somewhat  divided  in 
their  opinions  as  to  the  precise  state  in  which  sulphur 
is  introduced  into  the  air.  Mr.  Thomas  Wills,  F.  C.  S., 
in  a  lecture  delivered  before  the  British  Association  of 
Gas  Managers  (1878),  gives  as  his  opinion  that  "The 
sulphur  is  first  of  all  burnt  to  sulphurous  acid,  that 
then  a  certain  portion  of  this  sulphurous  acid  is  oxid- 
ized into  sulphuric  acid,  and  that  the  amount  so  oxid- 
ized depends  upon  circumstances;  but  that  given  a  suf- 
ficient length  of  time,  the  whole  of  the  sulphurous  acid 
will  be  oxidized  into  sulphuric  acid.  ]STow  as  to  the 
circumstances:  If  the  sulphurous  acid  is  kept  hot  in 
the  presence  of  moisture,  then  oxidization  goes  on  more 
rapidly;  if  it  be  cooled  down  almost  immediately  after 
it  is  formed,  the  action  is  very  slow,  and  within  any 


SULPHUR.  93 

reasonable  time  it  will  be  found  impossible  to  entirely 
oxidize  the  whole  of  the  sulphurous  acid  into  sulphuric 
acid.  Then,  secondly,  if  the  sulphurous  acid  meets 
with  a  base  or  with  an  easily-oxidizable  substance  with 
which  it  can  unite,  it  undergoes  oxidation  much  more 
readily  than  if  it  remains  in  a  state  of  free  acid. 

"From  my  own  experiments,  I  believe  that  under 
ordinary  circumstances,  considerably  less  than  one-half 
<>f  the  sulphurous  acid  produced  by  the  combustion  of 
coal  gas  is  oxidized  in  any  reasonable  time  into  sulphuric 
acid,  and  in  this  I  am  supported  by  several  gentlemen, 
who  not  being  connected  with  the  coal  gas  industry,  are, 
nevertheless,  thoroughly  acquainted  with  the  behavior 
of  sulphurous  acid  when  used  .in  the  manufacture  of 
alkali."' 

Mr.  AVills  also  makes  the  startling  statement,  in  the 
same  lecture,  that  if  we  regard  the  amount  of  coal  burnt 
in  London  as  eight  million  tons  per  annum,  and  we  take 
that  coal  to  contain  one  per  cent,  of  sulphur  which  is 
burnt — whether  in  the  form  in  which  it  is  sent  into  the 
houses  in  gas,  or  in  furnaces,  or  in  grates,  it  is  burnt  in 
some  way — and  which  is  a  low  average,  we  shall  have 
eighty  thousand  tons  of  sulphur  thrown  into  the  air  in 
the  form  of  sulphurous  acid,  and  if  that  is  calculated 
into  oil  of  vitriol,  it  will  amount,  in  one  year,  to  two 
hundred  and  forty  thousand  tons  of  oil  of  vitriol  senl 
into  the  atmosphere  of  London  alone  by  the  combustion 
of  coal. 

Though  the  amount  of  sulphur  in  the  aggregate 
appears  wry  large   from    the  figures   in  the  above  para- 


94 


COMBUSTION    OF    COAL. 


graph,  it  is  not  too  large  for  the  atmosphere  to  fully  take 
care  of  it  without  detriment  to  health  or  comfort,  but 
what  concerns  us  chiefly  in  our  present  line  of  inquiry 
is,  the  effect  of  sulphur  in  coal  upon  steam  boilers.  The 
corrosive  action  of  sulphur  compounds  on  iron  will  be 
found  in  Chapter  VIII. 


PRODUCTS  OBTAINED  FROM  COAL. 

BY  HENRY  A.  MOTT,  Jr. 


f  Naphtha 


I,  etc.  f 


f  Gas,   illum- 
inating, 
Tar. 
Coal.  \   Ammonia....  ( 

Water j 

Coke  for       ) 
fuel j 


Oils,  30 
per  ct 


"}J 


Used  to 
\  Benzole.  |  , 

j  Toluol..!  make 

^  J     [    Aniline. 

Naphtha Used  for  Varnishes. 

f  rnio   on  ..  I  Nylole Used  for  Small-pox. 

FURNISHES 

f  Carbolic  Acid  ")     (  Used  for  Disin- 
Creaylic  Acid.  J    1      fectants. 

Naphthalene l>yes,  etc. 

Anthracene,  %  per  ct.)  Used  to  make 

Chrysene )      Alizarine. 

Pitch,  70  \  fused  for  Roofing  and  Pavements, 
per  ct.     f  1  Anthracene,  2  per  cent. 


Dead  Oil 


The  preparation  of  alizarine  from  anthracene: 

Anthraquinone. 


Anthracene. 


Acetic  Acid. 


Potassic 
bichromate. 


Ch  Hio      +      Oi  H*  O2     +      K2  Cm  Ot     =        Cm  H  O2     +  etc. 

Anthraquinone.  Bromine.  Dibromoanthraquinone. 


Ch  Hs  O2      +2     Br      =       Ch  He  Bn   O2        +    etc. 

Dibromoanthraquinone.        Potassic  hydrate.  Alizarine. 


Ch    He  Br2   O2      +       2  KHO       =  Ch   H8  Oi     +    etc. 

The  following  table  gives  a  list  of  the  products  ob- 
tained by  the  distillation  of  coal : 


PRODUCTS    OBTAINED    FROM    COAL. 


95 


NAME. 

FORMULA. 

GAS    OR    VAPOR. 

SPECIFIC   GRAVITY. 

BOILING   POINT. 

DEGREES. 

CENTIGRADE. 

1.000 

Hydrogen 

H 

0.0G9 
0.971 
1.1  OG 
0.590 
0.622 

Nitrogen 

N 
0 

N    11.; 
IIjO 

Oxygen 

Ammonia 

33 

Aqueous  vapor 

100 

Carbonic  oxide 

CO 
C  Ch 

0.967 
1.529 

Carbonic  anhydride 

109  (Fahr.) 

Cyanogen 

C  X 

S  O; 

1.801 
2.2112 

Sulphurous  anhydride. 

+13.09  (Fahr.) 

Carbon  disulphide 

C  Sj 

2.645 

47 

MARSH    CAS  SERIES. 

Methyl  hydride 

C  II. 

0.5596 

Ethyl  hydride 

CaHe 

]  .037 

Propyl  hydride 

CsHs 

1.522 

Butyl  hydride 

CiHio 

2.005 

9 

Amyl  hydride 

CsHii 

2. 189 

30 

Hexvl  hydride 

CeHw 

0.669 

65 

Octyl  hydride 

CsHis 

0.726 

108 

Deevl  hydride 

Cioir.-2 

158 

OLEPIA  N  l    c.a,   SERIES. 

.M.i  hvlene 

(  '   !  I: 

0.484 

39 

Ethylene  (olefiani 

•  Ml, 

0.9784 

Propj  l-'ii.-  (tritylene)... 

CsH« 

1.152 

—17.8 

Butylene 

(Mb 

1.936 

+35 

A  1  I  I  \  lelle 

CsHio 

2.419 

55 

Caproj  lene  |  hexylene} 

CeHw 

2.97 

id.:; 

(MIu 

3.320 

99 

06 


COMBUSTION    OF    COAL. 


NAME. 

FORMULA. 

GAS   OR   VAPOR. 
SPECIFIC   GRAVITY. 

BOILING   POINT. 

DEGREES 

CENTIGRADE. 

ACIDS. 

Hydrosulphocyanic   .... 
H  vdrosulphuric 

II  (C  N)S 

JUS 

II  (Cello)  0 

C20H6O3 

1.175 
1.065  (solid). 

0.7058 

2.070 

2.695 
3.179 
3.179 

4.147 
4.632 
4.42:; 
6.741 

Sp.Gr.H20=l 

1 .020 

.09613 

.921 

85 

R  osolic 

188 

Hydrocyanic 

H  C  N 

C7H80 
CsHioO 

0«IIfi 

('ills 

ChHio 

C9H12 

CioHh 

CioIIh 

CuHio 

CeH* 

C15H4 

H2(C6H5)N 

(CtiA,)N 

(ChITt)X 

(CtH^X 

(CaHu)N 

(C,IIis)N 

(CioHis)N 

(CiiH.7)N 

26.5 

Acetic 

120 

ALCOHOLS. 

Cresylic  alcohol 

203 

Phlorvlic  alcohol, 

BENZOLE  SERIES. 

Benzole 

82 

Toluole 

111 

Xylole 

120 

( 'umole 

148 

Cvmole 

175 

Xaph  thalene 

212 

Anthracene 

Melts  at  213 

Chrysene 

Pvrene 

Aniline 

182 

Pyridine 

115 

Picoline 

134 

Lutidine 

154 

170 

Parvoline 

188 

211 

230 

PRODUCTS    OBTAINED    FROM    COAL. 


97 


NAME. 

FORMULA. 

GAS  OR  VAPOR. 
SPECIFIC   GRAVITY. 

BOILING   POINT. 

DEGREES. 

CENTIGRADE. 

Viridine 

(Ci2H9)-N 

(C9H-)N 
(CioH9)N 
(CnHn)N 

(CJTs)N 

1.017 

251 

Leeoline 

235 

Lepidine 

260 

Cryptidine 

256 

Pyrrol 

(8) 


CHAPTER   V. 

COMBUSTION. 

Chemical  Attraction  —  Muriate  of  Zinc  —  Gunpowder  — Physical 
Changes — Chemical  Changes — Definite  Proportions — Multiple 
Proportions — Carbonic  Acid — Carbonic  Oxide — Law  of  Equiv- 
alents— Energy  of  Chemical  Separation — Nature  of  Combus- 
tion— Conditions  Necessary  to  Combustion — Luminosity — Igni- 
tion— Flame — Recent  Studies  of  Luminous  Flames — Rate  of 
Combustion — Temperature  of  Fire — Weight  and  Specific  Heat 
of  the  Products  of  Combustion — Available  Heat  of  Combustion 
— Efficiency  of  a  Furnace. 

Combustion — This  term  is  given  to  those  chemical 
combinations  in  which  there  is  a  rapid  union  of  an  ele- 
ment such  as  carbon,  or  hydrogen,  with  another  element 
— for  which  it  has  the  particular  chemical  attraction 
known  as  affinity — oxygen,  for  example;  this  combina- 
tion resulting  always  in  the  formation  of  a  new  com- 
pound which  does  not  have  the  properties  of  the  ele- 
ments of  which  it  is  composed.  This  union  is  generally 
accompanied  by  an  evolution  of  light,  and  always  of 
heat. 

Oxygen  is  the  great  supporter  of  combustion  and  the 
chemical  reactions  of  atmospheric  air  are  due  to  the 
presence  of  this  gas  in  its  composition;  the  nitrogen 
present  being  inert  or  passive. 

Chemical  Attraction — This  force  is  distinguished  from 
other  kinds  which  act  within  minute  distances,  by  the 
complete  change  of  characters  which  follows  its  exer- 
tion, and  must,  from  its  very  nature,  be  exerted  between 


CHEMICAL    ATTRACTION.  99 

dissimilar  substances.  A  good  illustration  of  chemical 
attraction,  and  one  well  known  to  machinists,  is  that  of 
dissolving  zinc  in  muriatic  acid  to  make  a  soldering 
liquid;  atom  by  atom  it  yields  to  the  action  of  the  acid 
until  the  zinc  entirely  disappears;  as  a  result  there 
remains  a  liquid  having  neither  the  properties  of  the 
acid  nor  the  zinc — a  new  compound  has  been  formed. 

A  striking  illustration  of  the  difference  between  the 
effects  of  mechanical  intermixture  and  those  of  chem- 
ical combination  is  afforded  in  the  case  of  ordinary  gun 
powder.  (17).  In  the  manufacture  of  this  substance, 
the  materials  of  which  it  is  made — viz,  charcoal,  sul- 
phur and  nitre — are  separately  reduced  to  a  state  of 
tine  powder;  they  are  then  intimately  mixed,  moistened 
with  water,  and  thoroughly  incorporated  by  grinding 
for  some  hours  under  edge  stones ;  the  resulting  mass  is 
subjected  to  intense  pressure,  and  the  cakes  so  obtained, 
after  being  broken  up  and  reduced  to  grains,  furnish  the 
gun  powder  of  commerce. 

In  this  state  it  is  a  simple  mixture  of  nitre,  charcoal 
and  sulphur.  Water  will  wash  out  the  nitre,  bisulphide 
of  carbon  will  take  up  the  sulphur,  and  the  charcoal 
will  be  left  undissolved.  By  evaporating  the  water,  the 
nitre  is  obtained;  and  on  allowing  the  bisulphide  of 
carbon  to  volatilize,  the  sulphur  remains,  If,  however, 
we  cause  the  materials  to  enter  into  chemical  combina- 
tion, all  is  changed;  a  spark  lire-  the  powder:  the  dor- 
mant chemical  attractions  are  called  into  operation;  a 
large  volume  of  gaseous  matter  is  produced;  the  char- 


100  COMBUSTION    OF    COAL. 

coal  disappears,  and  no  trace  of  the  original  ingredients 
which  formed  the  powder  is  left. 

The  physical  and  other  changes  brought  about  by 
the  formation  of  new  compounds — a  result  of  chemical 
attraction — do  not  destroy  the  combining  elements,  but 
simply  re-arranges  them  in  another  form,  and  gives  to 
the  new  compound  properties  not  held  by  any  element 
singly. 

It  means  transformation,  not  destruction ;  no  matter 
how  much  the  substances  may  change  their  form,  the 
weight  of  the  new  products,  if  collected  and  examined, 
will  be  found  to  be  exactly  equal  to  that  of  the  sub- 
stances before  the  combination.  For  example:  the  com- 
plete combustion  of  hydrogen  and  oxygen  forms  water, 
having  properties  entirely  different  from  either  of  the 
two  gases.  Water  may  be  decomposed,  and  resolved 
into  the  two  gases  of  which  it  was  formed.  The 
weights,  combined  or  singly,  will  in  either  case  be  the 
same. 

Whenever  substances  unite  directly  with  each  other, 
heat  is  emitted,  and  varies  with  the  nature  of  the  sub- 
stances between  which  it  is  exerted.  In  general,  the 
greater  the  difference  in  the  properties  of  the  two 
bodies,  the  more  intense  is  their  tendency  to  mutual 
chemical  action ;  on  the  other  hand,  the  chemical  attrac- 
tion between  bodies  having  properties  closely  allied  to 
each  other  is  less  violent,  and  graduates  so  imperceptibly 
into  mere  mechanical  mixture,  that  it  is  often  impossible 
to  mark  the  limit, 


DEFINITE    PEO PORTIONS 


101 


Definite  Proportions — The  law  of  definite  proportions 
may  be  stated  as  follows  (17): 

In  any  chemical  compound  the  nature  and  the  propor- 
tions of  its  constituent  elements  are  fixed,  definite  and  inva- 
riable. For  instance,  100  parts  of  water  by  weight  con- 
tain 88.9  of  oxygen  and  11.1  of  hydrogen;  these  gases 
will  combine  in  no  other  proportions  to  form  water, 
and  any  excess  of  either  gas  will  remain  unchanged. 

When  two  or  more  compounds  are  formed  of  the 
same  elements,  there  is  no  gradual  blending  of  one  into 
the  other,  as  in  the  case  of  mixtures,  but  each 
compound  is  sharply  defined  and  exhibits  properties 
distinct  from  those  of  the  others,  and  of  the 
elements  of  which  the  compounds  are  composed. 
This  is  the  principle  in  the  law  of  multiple  propor- 
tions. 

There  are  two  compounds  of  carbon  and  oxygen 
commonly  known  as  carbonic  acid  (CO,),  and  carbonic 
•»xide(CO).  They  may  be  tabulated,  in  order  to  illus- 
trate what  has  just  been  said  in  regard  to  multiple 
proportions,  thus : 


BTMBOL. 

CARBON. 
PARTS   l;Y    WEIGHT. 

OXYGEN. 
PARTS    BY  WEIGHT. 

<  larbonic  oxide. 

<  larbonic  acid.... 

CO 

)  !i ». 

12 
12 

[6 

32 

It  will  be  observed  that,  the  quantity  of  carbon 
remaining  the  same,  the  quantity  of  oxygen  musl  be 
doubled  in  order  to  form  the  other  compound,  carbonic 


102 


COMBUSTION    OF    COAL. 


acid.  These  proportions  constitute  the  only  two  direct 
inorganic  compounds  of  carbon  and  oxygen.  It  is 
usual,  in  tabulating  proportions,  to  give  percentages  of 
the  composition  instead  of  atomic  weights ;  transposing 
the  above,  it  would  appear  thus : 


Carbonic  oxide. 
Carbonic  acid... 


CO 
CU 


ATOMIC  WEIGHT. 


28 
44 


42.86 


27^ 


57.14 
72.73 


For  an  extended  series  illustrating  the  law  of  definite 
proportions  of  two  of  the  constituents  of  coal  gas,  car- 
bon and  hydrogen,  note  the  many  combining  proportions 
in  the  marsh  gas,  the  olefiant  gas,  and  the  benzole  series? 
of  the  products  obtained  from  coal,  given  on  page  95. 

The  whole  table  is  one  of  great  interest  and  value  in 
connection  with  the  study  of  the  law  of  definite  or  mul- 
tiple proportions,  as  well  as  a  most  valuable  contribution 
to  the  chemistry  of  coal. 

Law  of  Equivalents — By  this  is  understood:  if  a  body 
— oxygen,  for  example — unites  with  certain  other  bodies, 
hydrogen,  carbon,  nitrogen,  sulphur,  etc.,  then  the  quan- 
tities by  weight  in  which  the  latter  substances  will  com- 
bine with  the  oxygen,  or  contain  multiples  of  these 
quantities,  they  represent  in  general  the  proportions  in 
which  they. can  unite  amongst  themselves. 

Hydrogen  combines  with  oxygen  in  a  smaller  propor- 
tion than  any  other  known  substance,  and  the  numbers 
representing  the  equivalents  of  all  other  bodies  may,  for 


LAW    OF    EQUIVALENT: 


103 


practical  purposes,  be  taken  without  material  error,  as 
multiples  by  whole  numbers  of  the  equivalent  of  hydro- 
gen (17). 

Table  XIII. 

Table  of  Elementary  Substances  Compiled  from  the  List  of  "Pro 
ducts  Obtained  from  ('oal.'  together  with  the  Symbol.  Spe- 
cific Grayity.  Atomic  Weight  and  Equivalent  Number  of 
Each. 


SYMBOL. 

SPECIFIC 
BBAVITY. 

ATOMIC 
WEIGHT. 

EQUIVALENT  NUMBER. 

H=l 

O=100. 

Bromine 

Br. 

C 

Cr. 

2.966 

3.52* 
6  onn 

80 
12 
52 
I 
14 
16 
39 
32 

80. 

6. 
26.27 

1. 
14. 

8. 
39. 
16. 

1000. 

Carbon 

75. 

'  hromium 

328.38 

ETydxi  gen 

H               .069 
X                .974 
0             1.106 
K               .860 
8              9  000 

12.5 

Xit  r<  igen 

175. 

Oxvgen 

100. 

Potassium 

187.5 

Sulphur 

200. 

The  equivalent  number  of  hydrogen  in  this  table  is 
1.  and  as  one  part  of  hydrogen  is  united  in  water  with 
exactly  eighl  part-  of  oxygen,  the  equivalent  number  of 
oxygen  is  8.  The  supposed  value  of  a  table  like  this 
is,  that  it  serves  to  Bhow  the  quantities  of  other  elements 
which  unite  with  eight  parts  of  oxygen,  and  it  also 
indicates  the  simples!  proportions  in  which  they  can 
unite  with  each  other. 

The  equivalent  numbers,  as  given  in  this  table,  are 
aeldom   \\->-'\,  and  the  reason  why  their  discontinuance 

Specific  gravity  of  :i  pure  diamond. 


104  COMBUSTION    OF    COAL. 

was  brought   about  was    explained   in   the   section    on 
atomic  and  molecular  weights,  page  8. 

Energy  of  Chemical  Separation — A  combustible  body 
like  coal  may  be  taken  as  a  fair  representative  of  poten- 
tial energy,  because  it  occupies  a  position  of  advantage 
over  a  non-combustible  body  in  this,  that  it  will  unite 
with  another  body  for  which  it  has  chemical  affinity 
like  oxygen,  and  this  energy  of  position  leading  as  it 
can  in  this  case,  to  a  process  of  chemical  separation 
during  the  act  of  burning,  in  which  we  have  potential 
energy  or  the  energy  possessed  by  the  coal  before  igni- 
tion, and,  the  energy  due  to  molecular  activity  by  reason 
of  the  act  of  combustion,  or  the  energy  of  motion 
changed  or  transmuted  into  another  form  of  energy 
represented  by  heat;  which,  if  we  choose,  may  then  be 
again  transformed  into  almost  every  other  form  of 
energy,  by  suitable  trains  of  mechanism,  or  other  meth- 
ods; remembering,  however,  that  every  time  a  transfor- 
mation takes  place  there  is  always  a  tendency  to  pass, 
at  least  in  part,  from  a  higher  or  more  easily  transform- 
able to  a  lower  form. 

The  energy  of  chemical  separation,  when  produced 
by  the  combustion  of  coal,  is  always  intense,  and  as  the 
observed  effects  are  so  much  below  the  theoretical  value 
ascribed  to  the  fuel,  it  would  seem  as  if  for  once  the 
law — if  there  is  one — of  conservation  of  energy  was  at 
fault.  But  this  is  not  the  case.  Our  methods  of  manip- 
ulation are  so  wasteful,  and  the  ordinary  construction 
of  furnaces  so  much  at  variance  with  the  ideal  furnace 


NATURE    OF    COMBUSTION.  105 

— whatever   that   may  be — that   a  large  percentage  of 
waste  can  be  directly  accounted  for. 

One  thing  with  reference  to  the  energy  of  chemical 
separation  is  certain,  and  that  is,  that  any  given  quan- 
tity of  carbon  or  other  combustible,  under  given  condi- 
tions, will  always  produce  the  same  quantity  of  heat. 

The  Xature  of  Combustion — "When  a  piece  of  rich 
bituminous  coal  is  thrown  upon  a  brisk  open  fire,  a  par- 
lor grate  for  example,  it  will  be  observed  that  physical 
changes  in  tnis  piece  of  coal  rapidly  occur.  First,  a 
disengaging  of  small  particles  of  coal,  which  are  often 
[•rejected  from  the  larger  piece  with  some  violence; 
then  a  swelling  or  puffing  out  of  the  exterior  surfaces  of 
the  coal;  jets  of  smoke  issuing  here  and  there,  proving 
themselves  to  be  rich  in  inflammable  gases,  for  soon 
they  burst  into  a  flame,  often  white  and  intensely  bril- 
liant near  the  coal,  fading  into  a  brownish  yellow  name, 
terminating  in  smoke.  Presently  the  piece  of  coal  will 
-how  indications  of  cleavage  and  may  split  itself  into 
two  or  mole  parts.  Sometimes  this  will  go  on  until  the 
whole  lump  disintegrates,  or  goes  to  pieces;  at  other 
times,  it  will  continue  to  swell,  expanding  to  much 
more  than  its  original  volume,  giving  off  its  gases,  and 
a  caking  process  is  undergone  until  the  whole  mass  is 
apparently  fused  together,  after  which,  the  volatile  por- 
tions of  the  coal  having  been  expelled  and  burned,  the 
remaining  portion  assumes  the  general  incandescent 
State  of  the  body  of  the  fuel  in  the  grate,  disappear- 
ing little  by  little  through  the  action  of  some  unseen 


106  COMBUSTION    OF    COAL. 

agency,  until  it  yields  up  all  its  combustible  substance, 
and  aslies  alone  remain,  to  mark  the  completeness  of  the 
change. 

It  would  be  interesting  to  know  what  became  of 
this  piece  of  coal.  If,  instead  of  throwing  the  whole 
piece  in  the  fire  a  portion  had  been  retained,  it  would 
probably  have  yielded  by  proximate  analysis, 

PEE  CENT. 

Fixed  carbon 60 

Volatile  combustible  matter 32 

Water 3 

Ash 5 

100 

The  thirty-two  per  cent,  of  volatile  matter  would, 
upon  farther  analysis,  be  found  to  consist  of 

Carbon;  Nitrogen; 

Hydrogen ;  Sulphur. 

Oxygen; 

The  particular  forms  in  which  these  elements  are 
usually  found  to  be  grouped,  are, 

Marsh  gas CH4 

defiant  gas C,  1I4 

Hydrogen H 

Carbonic  oxide CO 

Carbonic  acid C02 

Nitrogen N 

Ammonia NH3 

Sulphurous  oxide S02 

Bisulphide  of  carbon CS2 

Water H2  0 


NATURE    OF    COMBUSTION.  107 

and  many  hydrocarbons  not  given,  the  combinations 
of  these  two  elements  being  exceedingly  numerous;  of 
the  above,  nitrogen,  carbonic  acid,  ammonia  and  water, 
are  not  supporters  of  combustion. 

In  general,  carbon  and  hydrogen  are  the  elements 
meant  when  the  ordinary  term  fuel  is  used,  and'oxygen 
is  the  agent  by  which  they  are  made  to  yield  up  their 
heat.  It  is  the  chemical  union  of  these  elementary  sub- 
stances which  we  shall  designate  as  the  particular  form 
of  combustion  meant  wherever  the  word  occurs  in  this 
work. 

The  exact  nature  of  combustion  is  not  easily  stated. 
It  has  been  shown  elsewhere  that  coal  is  composed  of 
ultimate  particles  called  atoms,  also  that  atoms  of  differ- 
ent substances  are  attracted  toward  each  other.  Both 
the  carbon  and  hydrogen  in  coal  have  an  affinity  for 
oxygen  ;  before  they  unite  it  is  necessary  that  certain  con- 
ditions be  fulfilled.  In  the  case  of  coal  the  oxygen  has 
no  apparent  effect  on  it  at  ordinary  temperatures,  but 
once  the  coal  is  heated  to  the  point  of  ignition  the  oxy- 
gen will  unite  with  it,  and  Prof.  Tyndall's  theory  is: 
"Oxygen  having  a  choice  of  two  partners,  closes  with 
that  for  which  it  has  the  strongest  attraction.  It  first 
unites  with  the  hvdrogen  and  sets  the  carbon  free. 
Innumerable  solid  particles  of  carbon  thus  scattered  in 
the  midst  of  burning  hydrogen  are  raised  to  a  state  of 
incandescense.  The  carbon,  however,  in  due  time,  closes 
with  the  oxygen,  and  becomes,  or  ought  to  become,  car- 
bonic acid.'5  The  heat  and  lighl  produced  by  the  burn- 
ing of   coal    are  due,  according   to  his  theory,  to   the 


108  COMBUSTION    OF    COAL. 

collision  of  atoms  which  have  been  urged  together  by 
their  mutual  attractions. 

A  necessary  condition  to  the  burning  of  coal  is,  that 
there  be  a  considerable  mass  of  it  ignited  or  burning  in 
order  to  prevent  too  rapid  cooling ;  an  isolated  piece  of 
coal  will  not  burn  in  the  open  air,  because  the  tempera- 
ture will  soon  fall  below  the  point  of  ignition,  and,  as  a 
consequence,  chemical  action  will  cease;  but  an  ignited 
mass  of  coal  under  certain  conditions — the  combustion 
chamber  of  a  stove,  or  the  grate  surface  of  a  furnace, 
for  example — will  give  off  great  heat,  the  intensity  of 
which  will  depend  upon  the  quality  and  amount  of  coal 
burned,  but  ouce  the  hydrogen  and  carbon  having  united 
with  oxygen,  and  formed  by  their  union,  water  and 
carbonic  acid,  respectively,  their  mutual  attractions  are 
satisfied,  and  all  the  heat  has  been  given  off  that  is  pos- 
sible under  any  conditions. 

Whatever  may  be  the  real  nature  of  that  property 
of  matter  called  chemical  affinity  (34),  it  seems  to  be  a 
general  law  that  bodies  most  opposed  to  each  other  in 
chemical  properties  evince  the  greatest  tendency  to 
enter  into  combination,  and  when  these  chemically  dis- 
similar bodies  are  brought  together  under  favorable  con- 
ditions, one  very  important  fact  is  clearly  established 
with  regard  to  it,  and  that  is,  that  this  chemical  union  is 
always  accompanied  by  the  production  or  the  annihila- 
tion of  heat.  The  measurement  of  the  quantity  of  heat 
produced  by  a  given  amount  of  chemical  action  is  a 
problem  not  easily  solved,  but  it  may  be  expected  that, 
if  a  definite  quantity  of  carbon  be  burned  under  given 


NATURE    OF    COMBUSTION.  109 

circumstances,  there  will  be  a  definite  production  of  heat 
(26),  that  is  to  say,  a  ton  of  coals  or  of  coke,  when 
burned,  will  give  us  a  certain  number  of  heat  units,  and 
neither  more  or  less. 

CONDITIONS  NECESSARY  TO  COMBUSTION. 

Carbon,  hydrogen,  etc.,  will  combine  with  oxygen  in 
certain  definite  proportions  only.  The  combining  ele- 
ments must  be  in  immediate  contact,  not  the  contact 
which  we  usually  mean  when  powdered  or  liquid  sub- 
stances arc  mixed  together,  but  the  contact  which  chem- 
ical  affinity  denotes,  and  this  contact  must  be  at  a 
certain  temperature  in  order  to  produce  combustion. 
Carbon  and  oxygen  will  remain  in  mere  physical  con- 
tact any  length  of  time,  but  suppose  a  single  atom  of 
carbon  be  heated  red-hot,  combustion  will  begin  at  once 
and  continue  until  the  supply  of  either  one  of  the  ele- 
ments is  consumed  by  the  other.  There  is  no  element 
in  nature  which  has  not  an  affinity  for  some  other 
element,  but  it  does  not  follow  that  the  affinity 
existing  between  such  bodies  shall  be  accompanied 
by  the  evolution  of  light  and  heat  which  are  so  prom- 
inent in  the  combustion  of  coal.  The  oxidation  or 
corrosion  of  iron,  for  example,  in  which  a  body  of  iron 
in  anioist  atmosphere  combines  with  oxygen  and  hydro- 
gen, resulting  in  the  formation  of  a  new  compound, 
dors  so  with  a  slight  evolution  of  heat,  but  none  at  all 
of  light. 

All  solid  substances,  when  heated  sufficiently  high, 
emit    light.     This    light   may  be    more  or    less   intense, 


110  COMBUSTION    OF    COAL. 

according  to  the  temperature  of  the  heated  solid.  The 
temperature  at  which  bodies  begin  to  emit  red,  or  the 
feeblest  light  in  the  dark,  is  about  700°  Fahr.,  and 
increases  in  intensity  and  brilliancy  with  the  higher 
degree  of  heat,  until  it  passes  successively  through  the 
gradations,  red,  orange,  yellow  and  white  heat,  which  is 
the  highest  that  can  be  attained  in  the  furnace ;  bodies 
in  these  states  are  said  to  be  incandescent  or  ignited. 

Combustion  and  ignition  are  not  the  same  thing. 
The  ignition  of  solids  is  a  source  of  light:  the  combus- 
tion of  solids  is  a  source  of  heat.  Light  and  heat, 
though  apparently  governed  by  the  same  laws,  are  not 
identical.  The  combustion  of  hydrogen  with  oxygen 
produces  a  most  intense  heat,  yet  the  light  emitted  is  so 
feeble  as  to  be  scarcely  visible  in  daylight;  if,  however, 
a  piece  of  lime  be  introduced  into  the  flame  it  becomes 
so  intensely  brilliant  that  the  eye  can  not  bear  it.  This 
piece  of  lime  can  not  have  a  higher,  nor  indeed  so  high 
a  temperature  as  the  flame  itself.  The  particles  of  lime 
in  this  high  temperature  become  incandescent  or  ignited, 
and  are  the  source  of  the  light — if  the  lime  be  removed, 
the  intensity  of  the  light  is  gone,  but  the  heat  remains 
the  same ;  so  it  would  appear  that  ignition  is  the  glow- 
ing whiteness  of  a  body  caused  by  intense  heat,  or,  it  is 
a  consequence  of  combustion  instead  of  a  factor  in  it, 
the  particles  which  give  off  the  light  passing  away 
mechanically,  without  change  of  chemical  constitution ; 
on  the  other  hand,  it  is  the  chemical  change  in  the 
bodies   themselves,    and    the  formation    of    new    com- 


FLAME.  Ill 

pounds,  which  characterizes  combustion,  in  whatever 
form  it  may  appear. 

That  the  presence  of  two  bodies  is  necessary  to  com- 
bustion, is  very  neatly  illustrated  in  the  case  of  a  glass 
tube  containing  a  gas,  through  which  an  electric  spark 
is  to  pass  in  order  to  determine  its  spectrum.  If  a  single 
gas  would  burn  in  a  hermetically-sealed  tube  upon  the 
application  of  a  spark,  these  tubes  would,  after  the  first 
experiment,  be  unfit  for  the  purpose  designed;  yet  the 
spark  may  be  passed  through,  the  spectrum  determined, 
but  the  gas  remains  unchanged. 

We  have  already  seen,  in  the  first  part  of  this  chapter, 
that  if  combustible  substances,  such  as  charcoal,  sulphur 
and  saltpetre,  be  intimately  mixed  together,  and  the 
temperature  of  a  portion  of  the  mass  be  raised  to  the 
point  of  ignition,  the  combustion  is  so  rapid  and  violent 
thai  it  is  called  an  explosion.  The  combustion  in  this 
case  is  carried  on  independently  of  the  oxygen  of  the 
atmosphere. 

Flame — In  the  burning  of  wood  and  bituminous 
coal,  flame  is  a  marked  characteristic,  less  so  in  semi- 
bituminous,  and  almost  entirely  wanting  in  the  burning 
of  anthracite  and  charcoal.  Ordinary  flame  is  gas  or 
vapor,  of  which  the  surface,  in  contact  with  the  atmos- 
pheric air,  is  burning  with  the  emission  of  light.  The 
structure  of  flame,  in  general,  may  be  understood  by  a 
careful  study  of  that  produced  by  an  ordinary  lighted 
caudle,  :ui  illustration  of  which  is  ffiven   in  figure  1.     It 


112 


COMBUSTION   OF    COxVL. 


/' 


consists  of  three  separate  portions:  the 
inner  portion,  A,  nearest  to  and  surround- 
ing the  wick,  is  a  vapor  of  the  material  of 
which  the  candle  is  composed;  the  second 
portion,  B,  is  a  luminous  cone  which  envel- 
opes A,  and  is  that  portion  of  the  flame 
in  which  chemical  action  is  begun,  but 
which  does  not  seem  to  be  completed  until 
the  third  portion  of  the  flame,  marked  C, 
is  reached.  It  will  be  understood,  of  course, 
that  flame  does  not  consist  of  cones,  or 
envelopes  in  such  contrast  as  the  engraving 
would  seem  to  indicate;  this  is  for  the 
purpose  of  illustration  only.  The  explanation  of  the 
structure  of  this  flame  carries  us  back,  to  first  of  all,  the 
application  of  heat  to  melt  and  vaporize  the  combustible 


;  B 

2 


mm 


Figure  1. 


material  in  the  wick,  and  then  ignite  it.  The  consti- 
tuents of  the  candle  being  carbon  and  hydrogen,  the 
latter  being  more  easily  disengaged  and  set  free  than 
the  former,  and  having  a  greater  attraction  for  oxygen 
than  carbon,  unites  with  it  first,  and  forms  a  hydro- 
carbon flame  in  which  the  hydrogen  is  burning,  whilst 
the  particles  of  solid  carbon  in  the  flame  are  heated  to 
a  point  of  incandescence,  and  produce  the  light-giving 
quality  of  the  flame.  It  is  quite  probable  that  the  com- 
bustion of  the  carbon  is  completed,  if  at  all,  in  the 
outer  envelope  C,  in  contact  with  the  atmospheric  air 
from  whence  the  supply  of  oxygen  is  had.  It  is  not 
known  how  far  the  oxygen  penetrates  the  flame,  but 
judging  from    its  great  height,   as    compared  with  its 


FLAME.  113 

diameter,  it  is  quite  probable  that  it  is  largely,  if  not 
entirely,  confined  to  the  surface  of  the  cone  B ;  this  is 
inferred  from  the  soot  deposited,  and  lower  heat 
observed,  when  a  piece  of  card-board  is  passed  through 
the  flame  just  above  the  wick,  indicating  an  incomplete 
combustion,  which  is  not  observed  when  the  card-board 
is  held  in  the  apex  of  the  outer  cone. 

The  structure  and  appearance  of  flame  are  modified 
somewhat  by  the  density  of  the  gaseous  matter  burning, 
and  by  the  pressure  of  the  air  in  contact  furnishing  the 
oxygen.  This  is  quite  noticeable  in  the  case  of  steam 
boiler  furnaces  operated  with,  and  then  without,  a 
forced  draft.  Firemen,  as  a  rule,  judge  of  the  complete- 
ness of  combustion  by  the  appearance  of  the  surface  or 
flaming  portion  of  the  fire.  This  is  a  guide  which  often 
serves  a  good  purpose,  yet  it  does  not  reveal  the  whole 
secret.  It  is  possible  to  tell  how  nearly  the  prevention 
of  smoke  is  accomplished,  but  carbonic  oxide,  that 
arch-enemy  <>t'  economy  in  furnace  combustion,  may 
still  be  there.  The  admission  of  air  in  the  furnace 
above  the  grates  and  near  the  fuel,  serves  a  useful  pur- 
pose in  igniting  the  carbonic  oxide  as  it  rises  from  the 
mass  of  burning  coal;  this  flame,  as  exhibited  in  the 
burning  of  anthracite  coal  or  coke,  has  a  bluish  tinge. 
which  may  easily  be  distinguished  from  the  brownish- 
yellow  flame  produced  by  the  burning  of  coal  rich  in 
hydro-carhons.  However,  too  much  dependence  must 
not  be  placed  on  the  mere  appearance  of  flame,  either  in 
its  length  or  color. 
(9) 


114  COMBUSTION    OF    COAL. 

Pure  hydrogen  gas,  which  yields  a  most  intense  heat, 
burns  almost  without  visible  flame;  it  is  so  faintly  blue 
as  to  be  scarcely  luminous  in  full  daylight.  Perhaps  the 
best  illustration  of  colorless  flame  is  shown  in  the  ope- 
ration of  the  well  known  Buusen  gas-burner  as  fitted 
for  laboratory  uses ;  here,  the  glowing  solid  particles  of 
carbon,  which  give  character  to  hydrocarbon  flames,  are 
almost  entirely  wanting,  having  been  destroyed  by 
intense  heat  and  quick  combustion. 

It  would  be  impossible  to  give  a  description  of  flame 
which  would  be  of  the  slightest  service  in  determining 
what  is  going  on  in  the  furnace.  There  are  few  other 
than  experienced  persons  who  can  tell  the  color  of  flame 
in  a  mass  of  incandescent  fuel ;  but,  allowing  this  much, 
to  it  must  be  added  a  knowledge  of  color  and  form  of 
flame  characteristic  of  known  combustibles  when  per- 
fectly or  imperfectly  burned ;  this  only  leads  into  a 
labyrinth  of  difficulty  and  uncertainty  which  we  may 
well  keep  out  of,  and  endeavor  by  other  means,  much 
more  certain  and  reliable,  to  arrive  at  the  facts  sought 
after.  This,  of  course,  does  not  apply  to  the  observa- 
tion of  the  oxidizing  of  foreign  substances,  so  beauti- 
fully illustrated  in  the  Bessemer  process,  where  the 
flame  emitted  is  constantly  changing  until  the  impuri- 
ties are  gone,  and  the  brilliant  and  characteristic  light 
of  iron  alone  remains. 

RECENT  STUDIES  OF  LUMINOUS  FLAMES  (24). 

"For  a  long  time  Sir  Humphrey  Davy's  explanation 
of  the    luminosity  of  flames — that  it  was  due  to  the 


FLAME.  115 

presence  of  highly-heated  solid  particles — sufficed  for 
all  observed  phenomena.  A  serious  blow  to  its  suffi- 
ciency was  given,  however,  when  Frankland  discovered 
that  certain  flames  were  luminous  under  conditions 
which  left  no  reason  for  supposing  that  solid  matter 
could  be  present.  For  instance,  hydrogen  and  carbon 
monoxide,  burned  in  oxygen  under  a  pressure  of  ten  to 
twenty  atmospheres,  yield  a  luminous  flame  giving  a 
continuous  spectrum.  So  likewise  the  non-luminous 
flame  of  alcohol  becomes  bright  when  the  pressure  is 
increased  to  eighteen  or  twenty  atmospheres.  Frank- 
land  inferred  from  experiments  like  these  that  the 
luminosity  of  flames  was  due  rather  to  the  presence  of 
the  vapors  of  heavy  hydrocarbons,  which  radiate  white 
light,  than  to  incandescent  solid  matter. 

"Still  further  doubt  of  the  prevalent  theory  was 
raised  by  the  experiments  of  Ivnapp,  which  proved  that 
the  diminished  luminosity  of  a  flame  on  the  admission 
of  air  could  not  be  due,  as  had  been  supposed,  to  an 
oxidation  of  the  carbon  suspended  in  the  luminous  gas, 
since  the  same  effect  was  produced  when  nitrogen  or 
carbon-dioxide,  or  other  indifferent  gas,  was  used  as  a 
diluent. 

"Stein  and  Blochmann  attributed  this  effect  to  the 
direct  influence  of  the  diluting  gases  in  separating  the 
] (articles  of  carbon,  so  that  the  oxygen  of  the  air  might 
unite  with  them  more  quickly  than  under  the  ordinary 
circumstances  of  combustion.  Wibel  held,  on  the  con- 
trary,  that  the  diminished  luminosity  was  due  entirely 
to  tin;  absorption  of  heal  by  the  diluting  gas,  and  sup- 


116  COMBUSTION    OF    COAL. 

ported  his  view  by  some  very  ingenious  experiments. 
The  correctness  of  this  conclusion  has  been,  in  turn, 
controverted  by  the  later  experiments  of  Stein  and 
Heumann,  particularly  the  latter,  which  seem  to  show 
that  the  diminished  luminosity  consequent  upon  dilution 
is  due  not  solely  to  dilution  nor  wholly  to  the  cooling- 
action  of  the  added  gases,  but  to  both  these  causes  acting- 
together  and  frequently  supplemented  by  a  third  cause — 
namely,  the  energetic  destruction  of  the  luminous 
material  by  oxidation.  Heumann's  experiments,  which 
have  been  particularly  ingenious  and  careful,  lead  to  the 
following  results:  That  hydrocarbon  flames,  which 
have  lost  their  luminosity  by  the  withdrawal  of  heat, 
become  luminous  again  by  the  addition  of  heat;  that 
flames  rendered  non-luminous,  by  dilution  with  air  or 
indifferent  gases,  become  luminous  again  on  raising 
their  temperature;  that  flames  rendered  non-luminous 
by  excess  of  oxygen,  which  brings  about  energetic 
oxidation  of  the  carbon,  are  rendered  luminous  again 
by  diluting  the  oxygen  in  different  cases.  In  most 
cases  of  diminished  luminosity  two  or  all  of  these  causes 
are  at  work. 

"Another  unsettled  question  with  regard  to  flames 
has  been  the  cause  of  the  non-luminous  space  between 
the  opening  of  a  gas  burner  and  the  flame,  or  between 
the  wick  of  a  candle  and  the  luminous  envelope.  Bloch- 
mann  attributed  it  to  the  inability  of  the  surrounding 
air  to  mix  at  once  with  the  stream  of  gas  so  as  to  make 
it  combustible.  Benevines,  on  the  other  hand,  thought 
the  dark  space   due  to  the   mechanical  action    of  the 


RATE    OF    COMBUSTION.  117 

issuing  gas,  whereby  the  air  is  driven  to  a  distance  from 
the  orifice  of  the  burner — greater  or  less,  according  to 
the  pressure  on  the  gas,  leaving  a  space  wherein  the  gas 
is  deprived  of  the  requisite  amount  of  oxygen,  and 
consequently  remains  unburned.  Both  these  explana- 
tions are  shown  to  be  insufficient  by  the  single  circum- 
stance that  a  flame  never  directly  touches  any  cold  body 
held  within  it.  In  all  such  cases  Heumann  finds  an 
explanation  of  observed  conditions  in  the  cooling  effect 
of  its  surroundings — burner,  wick,  cold  iron,  or  what 
not — upon  the  gas.  For  a  certain  space  around  the 
cooling  body  the  gas  remains  at  a  temperature  too  low 
for  ignition. 

••  Where  the  gas  is-ues  under  high  pressure,  or  is 
greatly  diluted,  the  distance  of  the  flame  is  attributed 
partly  to  this  same  cooling  action  of  its  surroundings, 
but  more  especially  to  the  fact  that  the  velocity  of  the 
stream  of  gas  in  the  neighborhood  of  the  burner  is 
greater  than  the  velocity  of  the  propagation  of  ignition 
within  the  gas." 

Rate  of  Combustion — By  this  is  understood  the 
weight  of  fuel  that  can  be  burned  in  a  given  furnace  in 
a  given  time,  but,  as  applied  to  steam  boilers,  it  means 
the  number  of  pounds  of  coal  or  coke  which  can  be 
burned  per  square  foot  of  grate  surface  per  hour. 
Sometimes  the  rate  of  combustion  is  expressed  as 
pounds  of  net  combustible;  by  this  is  meant  the  pounds 
of  fuel  burned,  deducting  the  ashes  and  other  incom- 
bustible matter. 


118  COMBUSTION    OF    COAL. 

The  following  table  is  from  Professor  Rankine's 
"Steam  Engine,"  showing  the  rate  of  combustion  of 
English  coals,  with  a  chimney  draft ;  expressed  in 
pounds  burned  per  hour,  per  square  foot  of  grate  sur- 
face: 

POUNDS. 

1.  Slowest  rate  of  combustion  in  Cornish  boilers 4 

2.  Ordinary  rate 10 

3.  Ordinary  rates  in  factory  boilers 12  to    16 

4.  Ordinary  rates  in  marine  boilers 16  to    24 

5.  Quickest  rates  of  complete  combustion  of  dry  coal, 

the  supply  of  air  coming  through  the  grate  only..     20  to    23 

6.  Quickest  rates   of  complete  combustion  of   caking 

coal,  with  air-holes  above  the  fuel  to  the  extent 

of  1-36  of  the  area  of  the  grate 24  to    27 

7.  Locomotives 40  to  120 

Iii  the  experiments  carried  out  by  The,  Societe  Alsa- 
ciennes  de  Constructions  31ecaniques,  Mulhouse,  the  quan- 
tity of  Ronchamp  coal  burned  per  square  foot  of  grate 
surface  in  a  Lancashire  boiler  was, 

For  ordinary  firing 18.5    pounds. 

For  slow  firing... 10.15  pounds. 

For  heavy  firing 19.01  pounds. 

the  rate  of  combustion  between  slow  and  heavy  tiring 
being  almost  2  to  1 ;  in  regard  to  results :  the  quantity 
of  water  evaporated  being  expressed  in  equivalent 
evaporation  at  atmospheric  pressure,  and  from  a  tem- 
perature of  212°  Fahr.,  -was, 

For  ordinary  tiring 8.94  pounds  of  water. 

For  slow  firing 9.29  pounds  of  water. 

For  heavy  firing 9.06  pounds  of  water. 


RATE    OF    COMBUSTION. 


119 


During  the  Centennial  Exhibition  at  Philadelphia, 
1876,  eight  sectional  boilers  were  tested  : 

1.  To  ascertain  the  capacity; 

2.  To  ascertain  the  economy,  of  each. 

The  following  table  is  collated  from  the  published 
reports  of  the  trials : 

Table  XIV. 

Showing  the  Number  of  Pounds  of  Net  Combustible  (Lehigh  Coal) 
Burned  per  Square  Foot  of  Grate  Surface  per  Hour,  with 
Natural  Draught. 


GRATE 
AREA 
IN- 
SQUARE 
FEET. 

FOR   CAPACITY. 

FOR    ECONOMY. 

REFERENCE 

LEI  Mi: 

;n  SIG  HATING 

BOILER. 

POUNDS 

OF 
COMBUS- 
TIBLE 

PER 
HOUR. 

RATE  OF 
COMBUS- 
TION   IN 
POUNDS 
PEE 
HOUR. 

POUNDS 

OF 
WATER 
EVAPOR- 
ATED PER 
HOUR, 
FROM 
AND   AT 

212°. 

POUNDS 

OF 
COMBUS- 
TIBLE 

PER 
HOUR. 

RATE  OF 
COMBUS- 
TION   IN 
POUNDS 
PER 
HOUR. 

POUNDS 

OF 
WATER 
EVAPOR- 
ATED PER 
HOUR, 
FROM 
AND  AT 

212  . 

A 
B 
C 
D 
E 
F 
G 
II 

42. 

23. 

15.41 

42. 

27.5 

30. 

44.5 

36. 

613.9] 
378.07 
213.08 
490.77 
410.52 
373.25 
622.87 
478.46 

L4.62 
16.44 

13.83 
11.69 
14.93 
12.44 

14.(io 
13.29 

9.15 

9.89 
11.06 
10.41 

8.40 

9.97 
10.33 

9.57 

469.57 

260.16 

66.13 

341.71 

270.  SI 
248.59 
:;  5.57 
318.41 

11.18 

11.31 

10.78 
8.14 
9.85 
8.29 

8.89 

S.S4 

10.83 
10.93 
11.99 
12.09 
10.31 
10.04 
L1.82 
10.62 

For  anthracite  coal,  the  ordinary  rate  of  combustion 
under  stationary  boilers  maybe  taken  at  from  eight  to 
sixteen  pounds  per  square  fool  of  grate  per  hour. 

For  bituminous  coal,  from  ten  to  twenty  pounds. 


120  COMBUSTION    OF    COAL. 

In  locomotives,  Mr.  Forney  (11)  gives  the  maximum 
rate  of  combustion  at  about  one  hundred  and  twenty- 
iive  pounds  of  coal  on  each  square  foot  of  grate  surface 
per  hour. 

Temperature  op  Fire — The  temperature  of  combus- 
tion is  conditioned  upon 

The  nature  of  fuel  burned. 

The  nature  of  the  products  of  combustion. 

The  quantity  of  the  products  of  combustion. 

The  specific  heat  of  the  gases  present  in  the  furnace  resulting 
from  combustion;  this  includes  the  quantity  of  air  present  at  the 
moment  of  combustion  in  order  to  render  it  complete. 

The  principal  products  in  the  furnace  after  the  com- 
bustion of  coal  are, 

Carbonic  acid,  j 

Carbonic  oxide. 

Nitrogen. 

Air  furnished  in  excess,  and  unconsumed. 

Gaseous  steam. 

In  the  complete  combustion  of  one  pound  of  carbon 
we  have 

Carbon ] 

Oxygen 2.G7 

Total 3.(57  pounds  of  carbonic  acid. 

And  in  addition  to  this  there  would  be  present  in  the 
furnace  8.94  pounds  of  nitrogen  left  after  the  separation 
of  the  oxygen  from  the  atmospheric  air.  We  have 
then, 


TEMPERATURE    OF    FIRE.  121 

SPECIFIC  HEAT 

PRODUCTS.  POUNDS.  HEAT.  UNITS. 

Carbonic  acid £.67     X     .2164=       .794 

Nitrogen 8.94     X     -244    =     2.181 

Total,     2.975 

heat  units  absorbed  in  raising  the  temperature  of  the 
products  of  combustion  one  pound  of  carbon  1°  Fahr. 
The    combined    weight    of    the    two    products   are 
12. Gl  pounds. 


Then, 


Heat  units 2.975 

Tounds 12.(51 


.236 


their  mean  specific  heat. 

The  total  heat  of  the  combustion  of  carbon  is 
14,544  heat  units;  divide  this  by  the  2.975  heat  units 
absorbed,  we  have, 

^m=4889°  Fahr. 
2.975 

as  the  highest  theoretical  temperature  attainable  by 
the  complete  combustion  of  one  pound  of  carbon. 

This  is  allowing  11.61  pounds  of  air  per  pound  of 
carbon,  the  minimum  theoretical  limit. 

Suppose  that  eighteen  pounds  of  air  are  admitted 
to  the  furnace,  instead  of  twelve  pounds  (11.61),  and 
thai  tin'  combustion  is  complete,  the  temperature  and 
products  will  then  be, 

Carbon I 

<  >xygen 2.67 


122  COMBUSTION   OF   COAL. 

Nitrogen 8.94 

Air 6.39 

19.00 
We  then  have, 

SPECIFIC  HEAT 

PRODUCTS.                                                      POUNDS.                 HEAT.  UNITS. 

Carbonic  Acid 3.67     X     .2164=  .794 

Nitrogen 8.94     X     .244   =  2.181 

Air,  uncombined 6.39     X     -2377=  1.519 

Totals 19.00  4.494 


Then, 

4.494 


.237  mean  specific  heat. 


^4£r  =  3236°Fahr. 
4.494 


the  temperature  of  the  fire  being  1653°  less  than  the  first 
example,  showing  a  loss  of  33.81  per  cent. 

If  double  the  qauntity  of  air  (twenty-four  pounds) 
had  been  present  in  the  furnace  over  that  needed  for 
combustion  the  temperature  would  have  been  about 
2450°  Fahr.  These  examples  suffice  to  show  the  loss 
sustained  by  the  admission  of  too  much  air  in  the 
furnace. 

It  is  scarcely  necessary  to  remind  the  reader  that  the 
combustion  of  carbon  is  here  intended,  and  not  that  of 
coal;  this  is  mentioned,  merely,  to  explain  an  apparent 
discrepancy  in  the  next  table. 


AVAILABLE    HEAT    OF    COMBUSTION. 


123 


Table  XV. 

Showing  the  Weight  and  Specific  Heat  of  the  Products  of  Com- 
bustion, and  the  Temperature  of  Combustion"  (2). 


ONE   POUND   OF   COMBUSTIBLE. 


Hydrogen 

Olefiant  Gas 

Coal   (average) 

Carbon,  or  Pure  Coke 

Alcohol 

i . i _■  1  ■  i  Carbureted  Hydrogen 

.Sul]  ih  ur 

Coal,  with  Doable  Supply  of  Air. 


GASEOUS 

PP.ODUCTS    FOR   1   LI 

HEAT  TO 

RAISE 

MEAN 

TEMPER- 

WEIGHT. 

SPECIFIC 

ATURE 

HEAT. 

ONE 

DEGREE 

FAHR. 

POUNDS. 

\VATKK=1. 

UNITS. 

35.8 

.302 

10.814 

15.9 

257 

4.089 

11.94 

246 

2.935 

12.6 

236 

2.973 

10.09 

270 

2.080 

18.4 

268 

4.933 

5.35 

211 

1.128 

22.64 

242 

5.478 

TEMPERATURE 
OF 

COMBUSTION. 


FAHR. 

5744 ? 

5219 

4879 

4877 

4825 

4766 

3575 

2614' 


RATIO. 
100 

91 

85 
85 
84 
83 
02 
45 


Available  Heat  of  Combustion — The  available  heat 
of  combustion  of  one  pound  of  a  given  sort  of  fuel,  is 
that  part  of  the  total  heat  of  combustion  which  is  com- 
municated to  the  body  to  heat  which  the  fuel  is  burned ; 
for  example,  to  the  water  in  a  steam  boiler. 

The  efficiency  of  a  furnace,  for  a  given  sort  of  fuel,  is 
the  proportion  which  the  available  heat  bears  to  the 
toial  heat,  when  the  given  sort  of  fuel  is  burned  in  the 
given  furnace. 

The  word  "furnace"  is  here  to  be  understood  to 
comprehend,  not  merely  the  chamber  in  which  the 
combustion  takes  place,  bu1  the  whole  apparatus  for 
burning  the  t'ue]  and  transferring  heat  to  the  body  to  be 


124  COMBUSTION    OF    COAL. 

lieated,  including  ash-pit,  air-holes,  flame-chamber,  flues, 
tubes,  and  heating  surface  of  any  kind,  and  chimney. 

The  theoretical  heat  of  any  given  fuel  is  easily 
determined,  its  proximate  or  elementary  analysis  being 
known;  but  the  actual  available  heat  is  not  so  easily 
arrived  at,  and  can  only  be  determined  by  a  series  of 
more  or  less  elaborate  experiments  or  trials  in  actual 
use.  In  steam  boilers  the  efficiency  of  the  furnace  is 
measured  by  the  pounds  of  water  evaporated  per  pound 
of  coal  burned  on  the  grate,  under  known  conditions. 
This  will  always  be  found  to  be  below  the  theoretical 
quantity,  and  may  be  accounted  for  in  many  ways. 

Heat,  like  water,  or  steam,  must  flow  from  a  higher 
to  a  lower  level  in  order  to  become  available,  and  in 
this  flow  or  transfer  there  is  a  loss,  which  is  explained 
in  the  article  on  the  dissipation  of  energy. 

There  is  a  loss  due  to  the  radiation  of  heat  from  the 
sides  of  the  furnace ;  this  may  be  prevented  in  part  by 
building  hollow  walls  around  the  furnace. 

There  is  a  loss  in  the  use  of  cold  instead  of  heated 
air  for  supplying  the  oxygen  to  the  burning  fuel.  This 
may  be  remedied  in  part  by  forcing  the  air  through  the 
hollow  space  left  between  the  two  walls,  as  suggested  in 
the  preceding  paragraph. 

There  is  a  loss  occasioned  by  the  difference  of  tem- 
perature between  the  escaping  gases  and  that  of  the 
atmosphere  necessary  to  produce  natural  draft.  This 
may  be  largely  overcome  by  using  a  forced  draft,  and 
dispensing  with  a  chimney  altogether,  except  one  suffi- 
cient to  get  rid  of  the  noxious  gases ;  in  which  case  it 


AVAILABLE    HEAT    OF    COMBUSTION.  125 

will  act  as  an  outlet  only,  the  gases  being'forced  into  the 
open  air  by  a  pressure  behind  them,  and  thus  more  heat 
may  be  abstracted  from  them  than  if  the  temperature 
were  used  for  assisting  the  draft. 

There  is  a  loss  by  the  waste  of  unburned  fuel  pass- 
ing off  as  smoke,  and  that  falling  through  the  grates 
into  the  ash-pit  unconsumed. 

There  is  loss  by  imperfect  combustion,  that  is,  loss 
by  the  formation  of  carbonic  oxide  instead  of  carbonic 
acid. 

The  consideration  of  each  of  these  forms  of  loss  has 
been  undertaken  elsewhere  in  this  volume,  and  need  not 
In-  repeated  here.  There  is  no  method  by  which  the 
efficiency  of  a  furnace  can  be  exactly  determined, 
except  by  an  experimental  test  in  actual  service. 

The  quantity  of  water  evaporated  from  and  at  212° 
per  pound  of  coal,  varies  in  ordinary  practice  from  six 
to  ten  pounds:  ten  pounds  is  considered  a  very  fair 
evaporation,  and  is  probably  much  above  the  average  : 
this  is  about  seventy-one  per  cent,  of  the  theoretical,  if 
we  assume  fourteen  pounds,  as  the  average  theoretical 
evaporation  power  of  good  coal  and  coke. 

With  inferior  coal  the  results  would  be  farjbelow 
this;  the  quality  of  the  coal  or  coke  used  must  be  taken 
into  account,  as  well  as  the  construction  of  the  furnace, 
and  to  obtain  the  highest  results,  the  furnace  should 
have  its  details  arranged  with  special  reference  to  the 
burning  of  a  particular  fuel,  as  may  be  found  after  a 
trial,  the  best  and  most  economical  arrangement  for 
that  fuel. 


CHAPTER   VI. 

AIR  REQUIRED  FOR  FURNACE  COMBUSTION. 

Proportions  in  which  Oxygen  unites  with  Carbon  and  Hydrogen — 
Air  required  for  different  Fuels — Heated  Air  for  Combustion — 
Temperature  of  Air  supplied  to  Blast  Furnaces — The  Hoffman 
Kiln — Berthier's  Theory  in  regard  to  Heated  Air — Peclet's 
Observations — Prideaux'  Estimation  of  the  Value  of  Heated 
Air — Difficulties  in  Heating  or  Cooling  Air — Proportions  of  Fire- 
Brick  to  Fuel  burned  in  the  Siemens  Regenerative  Furnace — 
Ponsard  Furnace. 

The  conditions  under  which  coals  are  burned  are  so 
various  that  no  exact  quantity  of  air  can  be  specified 
which  will  supply  oxygen  enough  for  complete  combus- 
tion, and  still  preserve  the  minimum  dilution  of  gases 
passing  from  the  furnace  into  the  chimney.  The  quan- 
tity of  oxygen  required  for  the  complete  combustion 
of  any  given  quantity  of  carbon  or  hydrogen  has  been 
experimentally  determined,  and  is  well  known ;  the 
quantity  of  oxygen  present  in  atmospheric  air  being 
constant,  the  process  of  determining  the  amount  of  air 
required  for  the  complete  combustion  of  either  of  these 
two  substances  is  quite  simple. 

One  pound  of  hydrogen  gas  requires  eight  pounds  of 
oxygen  for  its  complete  combustion ;  this  requires  about 
thirty-six  pounds  of  air  to  furnish  it ;  the  product  of 
this  combustion  being  water  H2  0. 

One  pound  of  pure  carbon  (not  coal)  requires  two 
and  two-thirds  pounds  of  oxygen  for  its  complete  com- 


AIR    REQUIRED    FOR    FURNACE    COMBUSTION. 


127 


bustion,  requiring  about  twelve  pounds  of  air,  the  pro- 
duct of  combustion  being  carbonic  acid,  C02. 

One  pound  of  pure  carbon  (not  coal)  when  only  par- 
tially or  rather  imperfectly  burned,  so  as  to  yield  as  a 
product  carbonic  oxide,  CO,  instead  of  carbonic  acid,  CO,., 
requires  one  and  one-third  pound  of  oxygen,  furnished 
by  about  six  pounds  of  air. 

The  following  table,  by  Prof.  Rankine  (22),  shows 
the  theoretical  quantity  of  air  required  for  the  different 
fuels  of  which  the  analyses  are  furnished  : 


Table  XVI. 


FUEL. 

CARBON. 

HYDROGEN 

OXYGEN. 

AIR 
REQUIRED. 

I.    Charcoal — from  wood... 

0.93 

0  80 

0.94 

0.915 

0.87 

0.85 

0.75 

0.84 

U77 

0.70 

0.58 

0.50 

1 |  85 

11.16 

1  Ihabcoal — from  peat.... 

I  J.    Coke — good 

9.6 

1  L.28 

III.    <  !oal — anthracite 

0.035 

0.05 

0.05 

0.05 

0.06 

0.05 

0.05 

0.06 

0.020 

0.04 

0.06 

0.05 

0.08 

0.15 

0.20 

0.3] 

12.13 

Coal — dry  bituminous... 
1  !oal — caking 

12.H6 
11.73 

Coal — caking 

10.58 

Coal — can  n  el 

11.88 

(  !oal— dry,  long  flaming 
i  'ii  m, — lignite 

10.32 
9.30 

I  y      l'i  lt— dry 

7.68 

V     Wood — dry 

6.00 

VI.    Mineral  I  >n 

15.65 

The   quantity  of  air,  as  shown  in  the  above  table, 
represents  the  number  of  pounds  required  for  the  com- 


128  COMBUSTION    OF    COAL. 

plete  combustion  of  one  pound  of  the  fuel  named.  The 
intermediate  columns  show  the  proximate  constituents 
of  the  fuel. 

The  average  number  of  pounds  of  air  required  per 
pound  of  coke  and  coal,  appears,  from  the  above  table, 
to  be  a  little  less  than  11.5  lbs.  It  is  unnecessary  for 
practical  purposes  to  compute  the  air  required  for  the 
combustion  of  fuel  to  a  great  degree  of  exactness;  and 
no  material  error  is  produced  if  the  air  required  for  the 
combustion  of  any  kind  of  coal  and  coke  used  for  fur- 
naces is  estimated  at  twelve  pounds  per  pound  of  fuel. 
This  is  to  be  understood  as  the  theoretical  quantity ; 
practically,  about  twice  this  amount  is  supplied;  it  may 
be  approximately  stated  that,  three  hundred  cubic  feet, 
or  twenty-four  pounds  of  air,  are  supplied  to  burn  one 
pound  of  coal,  in  boiler  and  heating  furnaces  as  ordi- 
narily constructed. 

HEATED  AIR  FOR  COMBUSTION  (8). 

"  Nearly  all  the  processes  in  actual  use  for  economiz- 
ing fuel  have  for  their  leading  principle  that  of  pre- 
heating the  air  for  combustion.  This  is  a  pregnant  fact, 
of  which  many  instances  can  be  found.  When  Neilson 
made  his  invention,  or  rather  discovery,  in  1829,  he  began 
with  a  temperature  in  the  blast  furnace  of  50°  Fahr.,  and 
gradually,  in  succeeding  years,  raised*  it  to  600°  Fahr. 
By  1860  this  was  further  increased  to  750°  and  800°,  and 
from  1854  to  the  present  time  it  has  progressed  up  to 
1,100°,  1,400°,  and  more.  To  heat  the  great  volume  of 
air  for  a  large  blast  furnace  some  twenty  thousand  square 


HEATED    AIR    FOR    COMBUSTION.  120* 

feet  of  fire-brick  have  to  be  actively  employed.     A  gas 

furnace  is  simply  a  physical  impossibility  without  using 
air  raised  very  considerably  in  temperature  above  that 
of  the  atmosphere;  and  this  was  very  soon  found  out  by 
the  first  experimenters.  The  Hoffman  kiln,  which  has 
revolutionized  the  brick  trade,  is  highly  economical  i?4 
fuel,  mainly  because  the  air  for  combustion  is  intensely 
heated  by  first  passing  through  the  already  burnt,  incan- 
descent bricks.  In  Siemens'  regenerative  furnaces,  and 
in  the  furnaces  with  direct-acting  regenerators  of  the 
French  engineer,  Ponsard,  the  air  and  gases  for  combus- 
tion are  brought  to  high  temperatures  by  being  conveyed 
past  considerable  surfaces  of  brick,  heated  by  the  escap- 
ing fire-gases.  In  Boetius'  direct-acting  gas  furnaces* 
the  air  is  heated  by  being  passed  through  passages  ia 
the  brick  wall  of  the  producer  and  other  portions  of 
the  furnace.  In  Ireland's  and  in  Krigar  and  Grothe's 
cupolas  the  blast  is  heated  before  being  allowed  to  mingle 
with  the  products  of  combustion.  It  is  only  by  the 
application  of  Dr.  Geisenhcinier's  plan  of  usingveryhol 
blasl  thai  ii  is  possible  to  burn  American  anthracite  in 
the  blast  furnace.  The  functions  of  the  deflector  and 
the  fire-brick  arch  now  used  in  locomotive  engines  for 
burning  coal,  mainly  consist  in  heating  the  atmospheric 
aii'  aid  gases  for  e<>mbusti<>n.  On  the  London,  Brighton 
and  South  Coast  Railway  this  action  is  intensified  by 
working  with  the  ash-pan  almost  entirely  closed  up.  A 
Leading  feature  in  Mr.  T.  Symes  Prideaux's  contrivances 
for  economizing  fuel   consisted   in   predicating  tic  air. 

Several  contrivances  of  smaller  fame  could  be  cited  as 
(id) 


130  COMBUSTION    OF    COAL. 

depending*  for  their  success  on  the  use  of  more  or  less 
heated  air,  such  as  one  or  two  forms  of  puddling  fur- 
naces and  furnace  doors.  The  leading  feature  of  Mr. 
"W.  Gorman's  gas-furnace  is  that  of  heating  the  air  for 
combustion  by  means  of  the  escaping  fire-gases.  How- 
atson's  puddling  and  heating  furnaces,  of  which  a  great 
number  were  said  to  have  been  set  up  a  few  years  ago, 
is  another  instance  of  the  application  of  heated  air,  as  is 
also  in  great  measure  that  of  Mr.  Price.  A  furnace 
which  has  been  described  as  the  Newport  puddling  fur- 
nace may  be  said  to  be  on  a  partially  regenerative 
system. 

"  One  obvious  reason  to  account  for  the  effect  of  the 
heated  air  in  raising  the  intensity  of  combustion,  is  the 
mere  fact  of  the  attendant  elevation  of  temperature.  A 
current  of  air  sufficient^  hot  can  set  wood  or  coal  on 
tire.  But  there  are  several  more  recondite  reasons  than 
this.  In  the  first  place,  a  very  high  temperature  of  the 
air  for  combustion  acts  as  a  corrective  whenever  too 
little  or  too  much  air  is  introduced.  The  French  savant, 
Berthier,  gave  another  reason,  which  would  partly 
account  for  several  points  noticable  in  the  practical 
working  of  furnaces.  It  is  based  on  the  very  probable 
hypothesis  that  the  chemical  affinity  of  heated  air 
for  carbon  is  much  greater  than  that  of  cold  air.  As 
observed  by  Peclet,  one  consequence  is,  that  when  heated 
air  is  employed,  it  is  deprived  of  oxygen  within  a  very 
short  travel.  The  combustion  is  thereby  more  concen- 
trated and  localized  at  the  focus  where  the  heat  has  to 
be  applied  and  to  do  its  work.     At  the  spot  required 


HEATED    AIR   AND    CHEMICAL    ACTION.  131 

the  heat  is  higher,  and  at  the  same  time  beyond  it  lower. 
These  two  circumstances  are  favorable  to  the  economy 
of  fuel,  for  combustion  and  high  temperature  beyond 
the  point  where  heat  has  to  be  applied  are  useless.  It 
has  thus  been  found  in  practice  that  the  greater  the 
affinity  of  any  fuel  for  oxygen,  the  lower  need  be 
the  temperature  of  the  air.  It  is  hence  used  at  a 
lower  heat  in  charcoal  furnaces  than  in  coke  blast 
furnaces,  and  less  in  the  latter  than  in  furnaces  fed 
with  anthracite.  This  explains  the  fact,  which  has  been 
found  on  trial,  that  a  reverberatory  furnace,  supplied 
with  hot  air  at  the  grate  only,  has  actually  been 
found  to  have  its  efficiency  diminished,  and  not 
increased.  The  gaseous  combination  or  chemical  union 
being  thereby  accelerated,  the  combustion  takes  place 
more  on  the  grate  and  less  in  the  body  of  the  furnace, 
where  the  actual  work  has  to  be  done. 

HEATED  All;  AND  CHEMICAL  action. 

"While  heating  the  air  for  combustion  intensifies  the 
chemical  affinities  between  the  air  and  the  fuel,  the  pro- 
ce6B  offers  another  most  effective  means  of  diminishing 
tic  consumption  of  fuel,  and  of  almost  indefinitely 
increasing  the  intensity  of  the  fire.  By  applying  the 
fire-gases — which  are  useless  where  they  are  only  equal 
in  temperature  t<>  the  goods  to  be  heated — to  pre-heat- 
ing  the  air  for  combustion,  an  actual  recuperation, 
returning,  or  carrying  back,  of  the  heat  is  caused. 
Thi-  amounl  saved  can  be  exactly  expressed  by  the  pro- 
duct of  the  weight  <'f  the   air   thus  returned  for  use  in 


132  COMBUSTION    OF    COAL. 

combustion  into  the  actual  temperature  given  it,  and  its 
specific  heat. 

"The  exact  mode  of  estimating  this  was  first  indi- 
cated by  Mr.  J.  S.  Prideaux,  and  adopted  by  Rankine. 
According  to  results  of  experiments  made  with  the  mer- 
curial calorimeter — of  course,  under  conditions  unrealiz- 
able in  practice — one  pound  of  carbon,  combined  with 
its  equivalent  by  weight,  or  two  and  two-third  pounds 
of  oxygen,  will  develop  fourteen  thousand  five  hundred 
British  units  of  heat,  or  will  raise  fourteen  thousand 
five  hundred  pounds  of  water  one  dcg.  Fahr.  But,  to 
effect  the  combination  in  the  atmosphere,  this  amount 
of  oxygen  has  to  be  taken  in  conjunction  with  the 
nitrogen  of  the  air.  amounting  to  nine  and  one-third 
pounds.  In  other  words,  the  very  least  amount  of 
atmospheric  air  used  in  combustion  is  twelve  pounds; 
it  is  in  many  furnaces,  especially  those  Avorking  with  a 
chimney  draught,  required  to  be  twice  as  much,  or 
twenty-four  pounds.  Assuming  the  most  probable  case, 
that  twenty-four  pounds  of  air  per  one  pound  of  carbon 
be  taken,  and  that  this  carbon  has  been  completely 
burnt,  then,  as  atmospheric  air  consists  of  eight  parts  by 
weight  of  oxygen  and  twenty-eight  of  nitrogen,  the 
products  of  combustion  resulting  from  the  one  pound 
of  carbon  and  the  twenty-four  pounds  of  air,  weighing 
in  all  twenty-five  pounds,  will  consist  of  three  and  two- 
third  pounds  of  carbonic  acid  and  twenty-one  and  one- 
third  pounds  of  inert,  uselessly  heated  nitrogen.  It  is 
clear  that,,  for  instance,  the  more  nitrogen  there  hap- 
pened   to   be   mingled   with    oxygen,   the    greater   the 


HEATED    AIR    AND    CHEMICAL    ACTIOX.  133 

weight  of  matter  that  would  have  to  be  uselessly  raised 
in  temperature;  and  that  the  greater  its  capacity  for 
absorbing  heat — the  greater  its  specific  heat — the  greater 
the  amount  of  heat  that  would  be  taken  up. 

"We  need  scarcely  observe  that  the  so-called  specific 
heat  of  any  body  is  that  amount  of  heat  which  it  absorbs 
or  gives  out  whenever  its  temperature  rises  or  falls 
respectively;  and  the  unit  of  measure  in  the  scale  of  spe- 
cific heat  is  that  of  water.  Thus,  the  speeific  heat  of 
carbonic  acid  gas  being  0.217  and  of  nitrogen  0.245,  the 
mean  of  three  and  two-third  pounds  of  the  first  and 
twenty-one  and  one-third  pounds  of  the  latter  is  <>._>-''>7  ; 
this,  multiplied  by  the  weight,  twenty-five  pounds,  and 
divided  into  the  fourteen  thousand  five  hundred  units  of 
heal  which  can  be  generated  from  a  pound  of  carbon, 
gives  2.440°  as  the  temperature  of  the  products  of  com- 
bustion, in  the  form  of  about  one  thousand  eight  hun- 
dred cubic  feet  of  fire-gases. 

"From  these  figures  alone  is  seen  the  paramount 
importance  of  thoroughly  heating  the  air  for  com- 
bustion, of  thoroughly  heating  its  oxygen  in  order 
to  facilitate  combination  with  the  carbon,  and  of 
liniinarily  heating  its  nitrogen  in  order  that  its  fourfold 
useless  volume  may  not  rob  the  heat  required  at  the 
very  moment  and  focus  of  combustion.  Now,  it  is 
evident  that  the  nearer  the  temperature  of  the  useless 

nitrogen  i-  raised  to  that  of  the    tire,  the   less   is  the    loss 

to  the  fire  in  unnecessarily  heating  it  while  it  i-  pai 
with  the  oxygen;  ami  whatever  of  this  can  he  done  by 


134  COMBUSTION    OF    COAL. 

means  of  the  very  escaping  gases  themselves  is  pure 
saving. 

"  The  very  great  difficulty  in  either  heating  or  cool- 
ing air  is  its  non-conducting  capacity,  or,  more  strictly 
speaking,  the  difficultly  in  obtaining  a  sufficiently 
rapid  convection  of  heat  to  and  from  the  mass  of  air 
employed.  This  is  too  well  known  to  all  contrivers  of 
hot-air  engines  or  of  air-cooling  machines;  in  cold  cli- 
mates it  constitutes  the  comfortable  properties  of  flan- 
nels and  furs.  To  heat  or  cool  air,  very  extensive  sur- 
faces, together  with  very  great  differences  of  tempera- 
ture, are  hence  absolutely  necessary.  We  believe  that 
the  Siemens  regenerators  are  proportioned  in  such-wise 
as  to  give  about  seventeen  pounds  of  fire-brick  for  each 
increment  of  gaseous  fuels  that  can  be  developed  from 
one  pound  of  coal.  As,  however,  only  about  one-fourth 
of  the  total  regenerative  capacity  is  being  heated  to  the 
full  temperature  of  the  gases  passing  down  through  the 
ports,  this  amount  has  to  be  increased  fourfold ;  so  that 
nearly  seventy  pounds  of  fire-brick  are  probably  used 
per  pound  of  product  of  combustion.  The  surface  of  a 
Ponsard  recuperator  for  an  ordinary  re-heating  furnace 
is  stated  to  average  twenty-three  square  metres,  half  of 
which  is  for  cooling  the  fire-gases,  and  the  other  half 
for  heating  the  air;  and  therein  the  air  is  stated  to 
attain  the  temperature  of  1,500°  Fahr.  When,  as  in 
the  Boetius  furnace,  the  sides  or  the  top  or  bottom  of 
the  furnace  are  used  to  heat  the  air,  the  air  is,  firstly, 
not  merely  heated,  but,  secondly,  it  serves  as  a  cooling 


HEATED    AIR    AND    CHEMICAL    ACTION.  135 

medium — protecting  the  brickwork  by  keeping  down 
the  temperature.  The  heat,  also,  that  would  otherwise 
be  uselessly  radiated  is  thus  picked  up  by  the  air  during 
its  circulation,  actual  trials  with  the  pyrometer  having 
shown  that  the  air  can  be  heated  in  this  way  up  to  600° 
Fahr." 


CHAPTER  VII. 

THE  FURNACE. 

Furnace  Draft — Sectional  Ana  of  Chimneys — Height  of  Chimneys 
— Volume  of  Escaping  Gases — Weight  of  Escaping  Gases — Tem- 
perature of  Escaping  Gases — Distribution  of  Air  in  the  Fur- 
nace— Admission  of  Air  Over  the  Fire  —  C.  Wye.  Williams 
Plan  — T.  S.  Prideaux'  Plan  — W.  A.  Martin's  Plan— Experi- 
mental Test  of  the  Mavtin-Ashcroft  Furnace  Door  at  U.  S. 
Navy  Yard,  Washington — Perforated  Pipes — Admission  of  Air 
at  the  Bridge-Wall- — R.  K.  McMurray's  Plan  for  Admitting 
Treated  Air — Admission  of  Air  and  Evaporation. 

Furnace  Draft  may  be  produced  by  any  one  of  the 
following  methods : 

1.  A  natural  chimney  draft,  or  that  due  to  the 
unbalanced  pressure  of  a  column  of  heated  gases.  This 
may  be  modified ; 

2.  By  the  use  of  a  jet  of  steam  escaping  into  the 
chimney  through  a  contracted  orifice,  by  which  an 
increased  draft  is  obtained  over  that  given  above ;  this 
may  be  either  "live"  steam  from  the  boiler  or  the 
exhaust  from  a  non-condcnsino:  engine. 

3.  By  a  forced  draft  produced  by  a  fan-blower,  or 
other  device. 

The  first  is  almost  exclusively  employed  in  con- 
nection with  stationary  steam  boilers.  The  object  of 
chimney  draft  is  to  supply  oxygen  to  the  burning  fuel, 
and  then,  to  get  rid  of  the  products  of  combustion. 

The  sectional  areas  of  chimneys  usually  bear  some 
empirical  relation  to  the  area  of  the  grate.     In  practice 


FURNACE    DRAFT.  187 


tlii-  sectional  area  varies  from  one-sixth  to  one-tenth  of 
the  grate.  After  a  series  of  elaborate  experiments  Mr. 
Isherwood  fixed  upon  one-eighth  of  the  area  of  the 
grate  as  being  the  best  proportion  for  draft  area,  and 
which  will  be  near  enough  for  the  area  of  chimneys  in 
any  ordinary  practice. 

The  height  of  the  chimney  is  often  determined  by 
the  character  of  the  surroundings,  such  as  buildings. 
hills,  etc.,  and  in  cities,  the  minimum  height  is  not  unfre- 
quently  fixed  by  local  legislation:  but  aside  from  this, 
there  is  a  great  deal  of  "ride  of  thumb"  about  it.  The 
building  of  a  chimney  costing,  say  from  two  thousand 
to  five  thousand  dollars,  is  designed  not  only  for  pres- 
ent, but  for  prospective  future  needs,  and  the  desire  is, 
thai  it  shall  be  amply  large  for  an  uncertain  future 
requirement. 

Within  reasonable  limits  there  is  no  objection  to  a 
large,  and  especially  a  high  chimney — other  things  being- 
equal — the  higher  the  chimney  the  better  the  draft. 

Furnace  draft  is  caused  by  the  difference  in  weight 
or  pressure  of  the  column  of  cold  air  outside  of  the 
chimney,  and  the  weight  of  the  column  of  heated  gases 
within  it.  Air  and  gases,  when  heated,  expand  in 
volume,  and  become  less  dense  than  for  equal  volumes 
at  a  lower  temperature;  this  difference  in  density  is  the 
draft-producing  quality  of  heated  gases.  The  increase 
in  volume,  tor  different  temperatures,  has  been  calcu- 
lated by  Professor  Rankin  e.  The  following  are  some  of 
the  results : 


138 


COMBUSTION   OF    COAL. 


Table  XVII. 

Showing  the  Volume  of  Escaping  Gases  in  Cubic  Feet  per  Pound 
of  Coal  Burned. 


POUNDS  OF  AIR  PER  POUND  OF  COAL. 

12  POUNDS. 

18  POUNDS. 

24  POUNDS. 

FAHR. 
32° 

68 

104 

212 

392 

572 

752 

1112 

1472 

1832 

2500 

CUBIC  FEET. 

150 
161 

172 
205 
259 

314 
309 
479 
588 
697 
906 

CUBIC  FEET. 

225 

241 

258 

307 

389 

471. 

553 

718 

882 
1046 
1359 

CUBIC  FEET. 

300 

322 

344 

409 

519 

628 

738 

957 
1176 
1395 
1812 

From  the  above  table  it  will  be  seen  that  if  225 
cubic  feet  of  air,  at  a  temperature  of  32°  are  necessary 
for  combustion,  it  will  require  241  cubic  feet,  if  supplied 
at  68°.* 

Supposing  241  cubic  feet  of  air  at  a  temperature  of 
68°  are  supplied  to  the  furnace  per  pound  of  coal  burned 
per  hour,  the  volume  of  escaping  gases  will  be  increased 
when  discharged  into  the  chimney  to  471  cubic  feet,  if 
the  temperature  of  the  escaping  gases  is  572°. 

*It  will  be  a  near  enough  approximation  in  this  case  to  assume  that  the  products 
of  combustion  and  air  will,  at  the  same  temperature,  occupy  similar  volumes. 


FURNACE    DRAFT.  139 


The  weight  of  escaping  gases  will  equal  the  weight 
of  the  air  and  the  combustible  portion  of  the  fuel.  At 
two  hundred  and  twenty-five  cubic  feet,  as  above,  there 
are  required  eighteen  pounds  of  air  to  one  pound  of 
combustible ;  the  increase  in  volume  from  two  hundred 
and  twenty-five,  to  two  hundred  and  forty-one  cubic  feet 
does  not  change  the  weight  of  the  air,  but  the  four 
hundred  and  seventy-one  cubic  feet  of  gases,  instead 
of  weighing  eighteen  pounds,  will  weigh  18  +  1  =  19 
pounds. 

We  <an  then  suppose  two  columns,  one  of  air  at  a 
temperature  of  68°  weighing  eighteen  pounds  and 
occupying  two  hundred  and  forty-one  cubic  feet,  and 
one  of  gases,  at  a  temperature  of  572°,  weighing  nine- 
teen pounds,  and  occupying  four  hundred  and  seventy- 
one  cubic  feet.  The  lighter  gases  being  confined  to  the 
chimney,  rise  to  the  top  by  virtue  of  their  lesser  gravity; 
tlie  higher  the  chimney,  and  the  higher  the  temperature 
of  the  escaping  gases,  the  stronger  or  more  intense  will 
be  i lie  draft. 

In  height,  chimneys  usually  vary  from  forty  to  one 
hundred  and  twenty  feet;  it  is  seldom  that  the  latter 
figure  is  exceeded,  and  when  it  is,  it  is  generally  for 
other  reasons  than  for  draft  simply.  .V  table  prepared 
by  Mr.  Theron  Skeel,  gives  the  relative  amount  of  coal 
that  can  be  burned  in  the  same  time,  with  chimneys  of 
various  heights,  as  follows: 

Height  of  chimney,  in  feel 120     100    80    60    40    20 

Relative  amount  of  coal 100      90    80    70    57    40 


140  COMBUSTION    OF    COAL. 

After  a  moderate  height  of  chimney  is  reached,  the 
effect  of  any  increased  height  is  very  small.  It  rarely 
occurs  that  a  height  of  more  than  one  hundred  feet  is 
needed  for  draft  even  when  permanent  chimneys  are  to 
be  built.  When  iron  chimneys  are  employed  the 
heights  commonly  vary  between  forty  and  seventy-live 
feet. 

Knowing  the  rate  of  combustion,  and  the  area  of 
the  chimney,  the  following  rule  of  Boulton  and  Watt 
for  determining  the  height  of  the  chimney  is  a  good 
one,  taking  into  account  all  the  uncertainties  attending 
chimney  proportions : 

Rule — Multiply  the  number  of  pounds  of  coal  con- 
sumed under  the  boiler  per  hour  by  twelve,  and  divide 
the  product  by  the  sectional  area  of  the  chimney  in 
square  inches  ;  square  the  quotient  thus  obtained,  which 
will  give  the  proper  height  of  the  chimney  in  feet. 

This  very  closely  approximates  Peclet's  formula,  so 
elaborately  presented  by  Professor  Rankine  in  his  treat- 
ise on  the  steam  engine,  and  to  which  the  reader  is 
referred  for  the  mathematics  of  chimney  proportions; 
also,  Weisbach's  Mechanics — DuBois — vol.  2,  part  2  ; 
or  Trowbridge's  Heat  and  Heat  Engines. 

The  connection  between  the  boiler  and  chimney 
should  be  as  short  and  direct  as  the  circumstances  will 
permit.  The  area  of  the  chimney  should  be  one-eighth 
of  the  grate.  The  grate  should  be  of  such  size  as  to  burn 
all  the  combustible  matter  without  loss,  and  without 
forcing  the  tire  beyond  the  point  of  economic  combus- 
tion. 


DISTRIBUTION   OF    AIR   IX   THE    FURNACE.  141 

The  best  temperature  for  the  escaping  gases  is  held 
in  practice  to  be  nearly,  but  not  quite,  that  sufficient 
to  melt  lead,  that  is,  a  temperature  a  little. below  600° 
Fahr. 

It  is  especially  worthy  of  remark,  that  a  moderate 
force  of  draft  through  the  fuel  seems  to  be  the  condition 
which  is  best  suited  to  the  fullest  economical  perform- 
ance, spied  and  power  both  considered,  of  the  semi- 
bituminous  and  bituminous  coals,  while  to  the  anthra- 
cites a  strong  current  is  best  adapted  for  the  same  ends. 

The  maximum  heating  effect  from  any  coal  is  pro- 
cured when  the  air  passes  through  it  fast  enough  to  burn 
entirely  all  the  combustible  matter  it  can  surrender  to  it 
by  its  <>\vn  beat:  but  when  the  current  exceeds  this  rate, 
its  influence  is  counteractive,  cooling  and  quenching  a 
portion  of  the  burning  matter,  and  driving  it  waste- 
full}'  forward,  with  the  combustion  not  completed.  The 
different  ignitibility  of  the  various  classes  of  fuel  sets, 
of  course,  different  limits  to  this  point  of  economical 
rapidity  of  blast  and  of  combustion — limits  which  are 
sooner  passed  with  the  bituminous  than  with  the 
anthracite  coals. 

Distribution  of  Air  in  tht  Furnaa — Air,  when  admitted 
through  the  ash-pit,  and  coming  in  contact  with  a  mass 
of  incandescent  coke  or  anthracite  coal  on  the  grate. 
yields  up  its  oxygen  and  combines  with  tin-  carbon  of 
the  fuel;  first,  in  the  proportion  to  form  carbonic  acid 
i  ('<)),  then,  in  passing  through  this  bed  of  ignited  fuel 
takes  up  another  equivalent  of  carbon,  and  converts  the 
carbonic  acid  (('<>•)  into  carbonic  oxide  (( !0). 


142  COMBUSTION   OF    COAL. 

Supposing  the  heat  units  of  the  net  combustible, 
when  burned  to  carbonic  acid,  to  be,  say,  14,000 ;  if 
burned  to  parbonic  oxide,  the  heat  units  would  amount 
to,  about,  4000,  showing  a  difference  of,  say,  10,000  heat 
units  per  pound  of  net  combustible,  or  more  than  sev- 
enty per  cent,  of  loss,  perhaps  waste  would  be  a  better 
word,  for  air  costs  nothing,  and  oxygen  is  all  that  is 
needed  to  effect  the  saving. 

The  distribution  of  air  above  and  below  the  fire  is 
intended  to  counteract  this  loss,  by  supplying  air  under 
the  grate  to  burn  the  fixed  carbon  or  coke,  and  above 
it,  to  supply  the  oxygen  needed  to  re-convert  this  car- 
bonic oxide  into  carbonic  acid. 

In  the  burning  of  a  coal  rich  in  hydrocarbons  smoke 
is  produced  in  large  quantities,  and  if  these  particles  of 
solid  carbon  are  mixed  with  carbonic  acid  gas  while 
still  in  the  furnace  and  at  a  high  temperature,  they  dis- 
appear as  smoke,  and  convert  the  carbonic  acid  already 
formed  in  the  furnace  into  carbonic  oxide,  by  3rielding 
up  their  carbon  to  the  heated  gas;  most,  if  not  all  of 
which,  might  have  been  prevented  by  slow  combustion, 
and  a  proper  supply  of  air  above  the  fuel. 

The  quantity  of  air  to  be  admitted  above  the  fire 
and  the  best  relative  position  for  its  admission,  is  a 
matter  of  furnace  detail  to  be  determined  and  fixed  by 
experiment,  rather  than  one  pertaining  to  the  theory  of 
combustion.  It  is  one  of  great  importance,  however, 
and  is  entitled  to  more  consideration  than  it  generally 
receives. 


THE    PRIDEAUX    FURNACE    DOOR.  148 

C.  WYE.  WILLIAMS'   FURNACE  DOOR. 

Mr.  Williams  has  given  this  subject  a  great  deal  of 
attention,  and  recommends  a  lire-door  consisting  of  two 
plates;  the  door  proper,  with  an  opening  through  it, 
and  another  plate  as  near  the  size  of  the  lire-door  open- 
ing as  possible  and  allow  the  door  to  be  closed ;  this 
plate  may  be  from  two  to  three  inches  back  of  the  lire- 
door  plate,  and  should  contain  as  many  perforations 
about  ~  inch  diameter  as  will  make  the  aggregate 
area  of  these  perforations  -i-  of  the  grate  surface. 

The  air  may  be  admitted  through  the  fire-door  into 
the  furnace  at  a  constant  rate,  or,  the  flow  of  air  may  be 
checked  by  the  closing  of  a  "butterfly"  register  on  the 
outside  of  the  door.  This  fire-door  has  worked  well  in 
practice,  especially  with  anthracite  coal. 

THE  PRIDEAUX  FURNACE  DOOR. 

Invented  by  Mr.  Thomas  S.  Prideaux,  England,  is 
represented  in  plate  I,  and  is  thus  described  in  the  speci- 
fication of  his  American  patent : 

"Tlii-  invention  relates  to  apparatus  for  regulating 
the  supply  of  air  to  furnaces  in  such  a  manner  as  to 
afford  the  furnace  an  additional  supply  of  air  after  coal- 
ing, which  supply  shall  gradually  diminish  and  eventu- 
ally cease  after  a  certain  definite  period  of  time  by  the 
action  of  an  automatic  apparatus,  thus  securing  the  cut- 
ting oft*  of  the  additional  supply  of  air,  when  no  Longer 
required,  independently  of  the  attention  of  the  fireman. 

■•  The  apparatus  consists  of  two  parts:  First,  a  case 
or  air-chamber  in   the  exterior  of  the  furnace,  furnished 


144  COMBUSTION   OF    COAL. 


with  a  flap  or  cover  moving  on  an  axle,  so  as  to  admit 
or  exclude  the  air  at  pleasure,  and  communicating  with 
the  interior  of  the  furnace  through  the  fire-door  and 
two  channels  placed  laterally,  the  exit-mouths  of  these 
passages  being  furnished  with  grating  suitable  for  heat- 
ing and  distributing  the  air  as  it  passes  into  the  furnace, 
and  at  the  same  time  preventing  the  radiation  of  heat  out- 
ward, while  the  throat  of  the  air-chamber  is  furnished 
with  a  damper  moving  on  an  axle,  which,  according  to 
the  angle  its  surface  makes  with  the  axis  of  the  line  of 
draft,  interposes  a  greater  or  less  impediment  to  the 
influx  of  air,  thus  affording  the  means  of  varying  the 
quantity  of  the  supply  according  to  the  character  of 
the  fuel  and  the  urgency  of  the  firing.  Secondly,  a 
motor-regulator,  by  which  the  gradual  closing  of  the 
lid  of  the  air-chamber  is  automatically  effected.  This 
motor-regulator  consists  of,  first,  a  cylindrical  cup  or 
cistern  pierced  with  a  small  orifice  at  the  bottom  and 
having  a  rod  rising  from  its  center;  secondly,  a  cast- 
iron  cylinder,  about  one  and  a  half  times  the  depth  of 
the  cistern,  and  sufficiently  larger  in  diameter  to  admit 
of  the  cistern  traversing  freely  within  it  when  the  appa- 
ratus is  charged  with  mercury,  and  having  a  cylindrical 
block  or  plunger  attached  to  the  under  side  of  the  cover, 
pierced  in  the  center  for  the  passage  of  the  cistern-rod, 
which  plunger  is  to  be  of  a  diameter  as  much  less  than 
the  interior  of  the  cistern  as  will  allow  of  the  free  pass- 
age of  the  mercury,  thus  enabling  the  cistern  to  be  rap- 
idly raised  to  the  top  of  the  cylinder. 


THE    PRIDEAUX    FURNACE    DOOR.  145 

"The  manner  in  which  my  said  invention  is  best  car- 
ried into  practice  ma}'  be  fully  understood  by  the  aid  of 
the  accompanying  drawing,  which  I  will  now  proceed  to 
ribe. 

"Figure  1  shows  a  front  elevation  of  an  apparat 
be  applied  to  the  mouth  of  a  furnace,  and  constructed 
according  to  my  invention.  Figure  2  is  a  cross-section 
of  the  same  through  the  line  A  B.  Figure  3  is  an  end 
elevation.  Figure  4  is  a  longitudinal  section  through 
the  line  C  D.  Figure  5  is  a  horizontal  section  through 
the  line  E  F,  and  Figure  6  is  a  hack  elevation  of  the 
said  apparatus.  Figures  7,  8,  9  and  10  are  hereinafter 
described. 

•■The  apparatus  works  as  follows:  The  charge  of 
mercury  is  placed  in  the  cistern  at  the  bottom  of  the 
cylinder,  and  the  cylinder-cover  screwed  down.  I  pon 
the  cistern  Vicing  raised  to  the  top  of  the  cylinder  the 
plunger  enters  the  cistern,  displacing  the  mercury  and 
causing  it  to  flow  over  its  sides  and  pass  down  the 
circumferential  interstice  to  the  bottom  of  the  cylinder. 
The  raising  of  the  cistern  is  effected  by  the  lifting  of 
the  lid  of  the  air-chamber,  while  the  weight  of  the 
latter,  slightly  depressing  the  cistern,  causes  the  mercury 
to  rise  in  the  circumferential  interstice  between  the 
cylinder  and  the  cistern  to  a  height  considerably  above 
the  level  of  the  bottom  of  the  cistern.  The  mercury,  as 
a  consequence,  flows  into  the  cistern  through  the  small 
orifice  in  a  time  proportionate  to  the  size  of  the  orifice, 
the  amount  of  the  charge  of  mercury,  and  the  force  of 
gravity  exerted  by  the  suspended  weight. 
(11) 


146  COMBUSTION    OF    COAL. 

"To  prevent  the  access  of  dust  or  steam  to  the 
interior  of  the  motor-regulator,  I  construct  a  closed 
channel,  I,  on  each  side  of  the  exterior  of  the  cylinder, 
extending  throughout  its  length,  for  the  passage  of  the 
side  rods  s  from  the  cross-head  k,  the  cross-head  itself 
being  covered  with  a  hood  or  cup,  o,  the  lower  edge  of 
which  is  in  apposition  with  the  upper  faces  of  the 
lateral  channels,  by  which  the  access  of  dust  or  steam  is? 
effectually  prevented. 

"An  alternative  plan  for  excluding*  the  entrance  of 
dust  or  steam,  compact  and  elegant  in  appearance,  but 
entailing  slightly  more  friction  and  requiring  greatei" 
delicacy  and  accuracy  in  workmanship,  is  to  construct 
the  cistern-rod  /  hollow,  so  as  to  enable  it  to  contain 
within  it,  and  travel  freely  upon,  a  small  tube,  u,  securely 
tapped  into  the  bottom  of  the  cylinder. 

"  This  tube  must  be  of  such  a  size  as  to  allow  of  the 
traverse  within  it  of  a  small  rod,  r,  which  may  be 
termed  the  connecting-rod,  attached  at  its  upper  end  to 
the  top  of  the  cistern  rod  (or  rather  tube)  by  a  pin- 
joint,  i,  and  at  its  lower  to  the  lid  of  the  air-chamber  by 
a  short  link. 

"To  enable  the  motor-regulator  to  sustain  a  heavier 
weight,  thus  lessening  its  liability  to  derangement  by 
friction,  and  at  the  same  time  affording  within  certain 
limits  the  means  of  varying  the  time  occupied  in  its 
descent,  I  apportion  the  depth  of  the  plunger  h,  cistern 
d,  and  cylinder  g,  so  that  the  edge  of  the  cistern  con- 
siderably overlaps  the  bottom  of  the  plunger.  As  the 
velocity  with  which  the  quicksilver  traverses  through 


THE    PRIDEAUX    FURNACE    DOOR.  147 

the  orifice  and  enters  the  cistern  increases  with  the  pres- 
sure, the  wider  the  range  of  pressure  available  the 
greater  the  power  of  varying  at  pleasure,  by  means  of 
movable  weights,  the  time  of  the  descent  and  the  closure 
of  the  air-valve. 

"To  prevent  the  interior  of  the  motor-regulator 
becoming  rusty,  thus  giving  rise  to  a  friction  which 
impairs  its  action,  I  heat  it  in  detached  pieces  to  a  tem- 
perature of  about  600°  or  700°,  and  then  plunge  it  iiitcr- 
warm  linseed-oil,  after  which  it  is  carefully  wiped  and 
then  thoroughly  washed  with  benzoline. 

"a  shows  the  exterior  air-case  divided  into  three 
chambers  or  passages,  6,  the  cover  or  damper  connected. 
by  a  liuk  to  the  connecting-rod  attached  to  the  cistern- 
rod  of  the  motor-regulator  or  cylinder  g.  The  cover 
or  damper  b  of  the  air-chamber  may  be  opened 
by  the  fireman  when  he  closes  the  door  after 
coaling,  hut  I  prefer  to  make  it  self-opening  by  the 
aid  of  the  segment  of  a  screw,  y,  formed  on  the 
hinge  of  the  furnace-door,  which  raises  a  lifting-bar, 
z,  upon  the  door  being  opened,  c  is  the  grating  for 
heating  and  finely  dividing  the  air  on  its  passage  into 
the  furnace,  and  at  the  same  time  assisting  in  conjunc- 
tion with  the  plates  of  sheet-iron  /  (having  vertical  slits 
or  openings  so  placed  that  the  intervals  shall  not  corres- 
pond), to  prevent  the  passage  of  the  radiant  heat  out- 
ward. />  is  the  flap,  the  office  of  which  is  to  vary  the  size 
of  the  neck  of  the  air-chamber,     w'  is  a  movable  weight 

suspended  from  the  tip   of  the    link,  which    attaches  the 


143  COMBUSTION    OF    COAL. 


connecting  rod  to  the  cover  of  the   air-chamber,  and 
which  is  furnished  with  a  small  hole  for  the  purpose. 

"Figure  7  shows  a  vertical  section  of  the  motor-reg- 
ulator with  a  hollow  cistern -rod.  Figure  8  is  a  horizon- 
tal section  of  the  same,  g  is  the  cylinder ;  d,  the  cup  or 
cistern,  h  is  the  plunger,  which  displaces  the  mercury, 
and  causes  it  to  flow  over  the  rim  of  the  cistern  into  the 
cylinder  when  the  cover  of  the  air-chamber  is  raised. 
/  is  the  hollow  cistern-rod;  e,  the  orifice  for  the  passage 
of  the  mercury;  u,  the  tube  tapped  into  the  bottom  of 
the  cylinder;  w,  a  weight,  advantageously  placed  to 
assist  by  its  gravity  in  overcoming  any  friction  opposing 
the  closing  of  the  apparatus;  o,  the  hood  or  cap  for 
excluding  dust  and  steam,  m  is  the  connecting-rod, 
and  i  its  pin-joint.  Figure  9  shows  a  vertical  section  of 
the  motor-regulator,  with  a  cross-head  and  closed  chan- 
nels for  the  passage  of  the  side-rods.  Figure  10  is  a 
view  of  the  same,  seen  from  above,  showing  the  hood  or 
cap,  and  the  channels  for  the  passage  of  the  side-rods. 
g  is  the  cylinder;  d,  the  cup  or  cistern;  h,  the  plunger; 
/,  the  cistern-rod ;  e,  the  orifice  for  the  passage  of  the 
mercury;  o,  the  hood  or  cap  for  excluding  dust  and 
steam;  k,  the  cross-head;  s,  the  side-rods,  and  I  the 
channel  for  the  passage  of  the  side-rods." 

THE  MARTIN  FURNACE  DOOR. 

The  furnace-door,  of  which  Figure  2  is  a  sectional 
representation,  is  the  invention  of  Mr.  "W.  A.  Martin,  of 
England,  and  is  now  being  introduced  in  this  country 
by  the  Ashcroft  Manufacturing  Company,  Boston,  Mass. 


T.  S.PRIDEAUX. 
APPARATUS    FOR    REGULATING    THE  SUPPLY   OF  AIR 

TO  FURNACES. 


FIG.%. 


FIG,  3 


■ 


THE    MARTIX    FURNACE    DOOR. 


140 


Tlii-  door  consists  in  the  combination  of  a  furnace  door, 
pivoted  on  a  horizontal  axis,  at,  or  near,  its  upper  ed 
and  made  to  open  and  close  by  being  swung-  pendulum- 
like through  the  lower  are  of  a  circle,  and  a  counterbal- 
ancing- weight  for  retaining  the  door  in  the  desired 
position. 


Fk;v 

By  this  door  a  Pew  inches  inwardly  tl 

LS  caused  to  outer  and   pass  among  the  fuel,  and  to  min- 

.vith  the  gases  proceeding  therefrom  in  the  pro 
of  combustion  alter  they  rise  from  the  fuel,  thus  causi 
them  to  unite  and  to  be  consumed  before  leaving  the 

L  of  !e/\  ing  it  in  the  condition  of  sm< 
or  unburned  and  by  opening  it  outwardly  to  the 

required  extent,  ample  i  rovision  is  made  for  '.lie  inser- 
tion of  the  fuel. 


150 


COMBUSTION    OF    COAL. 


Experiments  were  made  at  the  Washington  Nav}- 
Yard,  in  1874-5,  to  determine  the  relative  economy  of 
this  furnace-door,  over  the  ordinary  door,  the  latter 
being  that  recommended  by  C.  Wye.  Williams,  and 
described  on  page  143. 


Figure  3  is  a  representation  of  a  front  view  of  the 
boiler,  as  fitted  with  the  experimental  door,  and  the 
following  table  gives  the  comparative  results: 


THE    MARTIN    FURNACE    DOOR. 


151 


H«j 

30 

y,  i- 

k2 

CI 

C     5C 

r>  o  a 

n 

3  S»  I 

5  y. 

— 

•M     — 

x    33 

c 

1-1 "~  i-- 

a  x 
■-  a 

o  O  0 
S3° 

r-r 

cs 

x  < 

■«    5 

H  $ 

•< 

x:«  2    X 

lO 

g 

s  ^  + 

CM      C3 

_ 

c   —   c   S>  cs 

fc; 

a*   2    - 

■     l£b     *0     C.     OD 

CO   «D    00    tH    c 

U  O  3 

co  « 

C-.     —             «5 

=  -a 

I- 

C     —            IC 

a 

a 

<    5 

■< 

< 

H 

B 

•-    g 
a  g  2 

»  N*^?g  o 

1- 

»   13    U            -r 

:- 

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1-     CM 

cm  cm 

00 

CO    o 

3 

r.    /. 

-   i~   re    - 

x 

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« 

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s. 

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■*    r-             CM 

:: 

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nil 

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=    52? 

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a 

a 

a 

B 
r 

= 

r- 

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2 

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CD 

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5 

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5    : 

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V.     o 

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c- 

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U 

P- 

152  COMBUSTION    OF    COAL. 

The  boiler  with  which  these  experiments  were  made 
is  of  the  cylindrical,  horizontal,  tubular  type,  seventeen 
feet  eight  inches  long,  six  feet  in  diameter,  containing 
one  hundred  and  fifty-seven  brass  tubes,  ten  feet  long';, 
and  two  and  one-fourth  inches  outside  diameter;  having' 
two  furnaces,  with  a  combined  grate-surface  of  twenty- 
two  square  feet;  and  a  heating-surface  of  nine  hundred 
and  twenty-eight  square  feet. 

The  doors  have  an  opening  of  one  hundred,  and 
eighty-six  square  inches  each,  and  are  constructed  in  the 
usual  manner,  with  an  outer  shell  of  cast-iron,  contain- 
ing seven  one  and  one-fourth  inch  holes,  and  with  an 
inner  plate  of  wrought  iron  with  a  space  between  them 
of  three  inches,  the  inner  plate  being  perforated  with 
small  holes  through  which  the  air  is  distributed  over 
the  fuel. 

Perforated  Fipes — Instead  of  admitting  the  air 
through  the  furnace  door,  as  described  in  the  preceding- 
pages,  it  is  sometimes  admitted  through  the  sides  of  the 
furnace  above  the  fuel,  and  sometimes  back  of  the 
bridge-wall;  perhaps  the  device  most  frequently  used 
for  this  purpose  is  a  cast-iron  pipe,  about  six  inches  in 
diameter,  and  perforated  with  small  holes;  the  deter- 
mining of  the  aggregate  area  of  these  perforations  does 
not  seem  to  rest  upon  anything  in  particular,  and  is 
almost  entirely  a  matter  of  caprice;  this  pipe  extends 
into,  or  through,  the  combustion  chamber  under  the 
boiler,  and  is  built  into  the  walls,  the  ends  of  the  pipe 
being  left  open  to  the  air.  Whenever  a  device  of  this 
kind  is  employed  it  should  never  be  far  removed  from 


ADMISSION    OF    AIR   AT    THE    BRIDGE-WALL.  153 

the  bridge-wall,  and  it  is,  at  best,  of  doubtful  utility  if, 
by  this  means,  an  excess  of  cold  air  is  allowed  to  pass 
into  the  chamber  back  of  the  bridge-wall;  for  it  should 
be  remembered  that  oxygen  alone  is  not  what  is  needed, 
but  a  high  temperature  also,  to  insure  the  ignition  of 
the  carbonic  oxide,  which  is  the  only  reason  for  its 
admission  at  all. 

Admission  of  Air  at  the  Bridge-wall — The  admission 
of  air  at  this  particular  point  is  intended  to  supply  the 
oxygen  needed  to  complete  combustion  in  case  it  should 
be  imperfect,  while  the  gases  are  still  at  a  high  tempera- 
ture. A  very  successful  device  for  the  admission  of 
heated  air.  near  the  point  of  the  generation  of  gases  in 
the  furnace,  was  patented  by  Mr.  R.  K.  McMurray, 
New  York  City,  and  is  shown  in  plate  II. 

"The  improvement  consists  in  combining  with  the 
furnace  and  combustion  chamber  a  hollow  cast-iron 
tire -bridge,  formed  of  a  series  of  plates  united  together 
and  resting  on  the  top  of  a  bridge-wall  of  the  ordinary 
construction,  without  being  imbedded  therein,  into 
which  hollow  bridge  fresh  air  for  supply  to  the  combus- 
tion chamber  is  introduced,  and  within  which  it  is 
heated  to  a  temperature  approximating  to  that  of  the 
gases  escaping  from  the  furnace,  and  is  thence  delivered, 
in  a  minutely  divided  condition,  to  the  gases  as  they 
r  the  combustion  chamber.  The  improvement  fur- 
ther consists  in  such  construction  of  the  fire-bridge  as  to 
provide  ample  resistance  against  blows  or  shocks,  and 
the  effects  of  expansion  and  contraction,  as  well  as  to 
render  it  capable  of  being  readily  and  quickly  removed 


154  COMBUSTION   OF    COAL. 

from  its  position  in  the  setting,  renewed  or  repaired  at 
a  comparatively  slight  expense,  and  replaced  in  position 
for  further  operation. 

"  The  construction  of  the  tire-bridge  and  its  applica- 
tion in  the  setting  of  a  return  tubular  stationary  boiler, 
are  clearly  shown  in  the  accompanying  illustration.  It 
consists  of  a  fire-plate  A,  a  back  or  base-plate  B,  and  a 
dispersing-plate  C.  The  plate  A  is  corrugated  in  order  to 
give  it  increased  strength,  and  allow  for  expansion  and , 
contraction  under  change  of  temperature,  and  is  pro- 
vided with  a  light-bottom  flange,  which  rests  upon  the 
bridge-wall,  and  thence  rises  vertically  for  about  two- 
thirds  of  its  height,  at  which  point  it  is  inclined  at  an 
angle  of  about  forty-five  degrees.  The  bottom  plate  B 
conforms  in  the  relative  position  of  three  of  its  sides  to 
the  plate  A,  and  terminates  below  in  a  horizontal  foot. 
The  plates  A  and  B  are  connected  by  bolts  passing 
through  thimbles,  so  as  to  form  a  hollow  case.  The 
perforated  diffusing-plate  Cis  inserted  in  grooves  formed 
in  the  other  plates.  Ar  series  of  air-supply  openings  D 
are  formed  in  the  plate  B,  near  tlie  base ;  above  them 
extends  a  deflecting  flange,  E.  The  bridge  so  set  that 
the  lower  edge  of  the  fire-plate  A  is  slightly  below  the 
level  of  the  grate-bars,  and  its  ends  are  closed  by  the 
side  walls  of  the  setting,  or  by  metal  plates  fitted 
therein;  the  latter  arrangement  allowing  of  the  bridge 
being  removed  when  desired  by  drawing  it  out  longi- 
tudinally through  the  opening  in  the  side  wall. 

"The  fresh  air  enters  the  space  between  the  back 
plate  and  the  fire  plate  through  the  supply  openings  D 


m'murray's  bridge-wall.  155 

and  is  deflected  by  the  flange  against  the  heated  surface 
of  the  fire-plate,  and  thence  passes  upward,  as  indicated 
by  the  arrows,  figure  2,  along  the  space  between  the 
two  plates.  The  air  is  thus  introduced  in  a  minuteh' 
divided  condition  into  the  combustion  chamber  at  a 
temperature  closely  approximating  that  of  the  gases 
.■scaping  from  the  furnace.  It  mingles  with  these  gases 
and  oxidizes  the  carbonic  oxide,  effecting  complete  com- 
bustion with  a  corresponding  economy  of  fuel  and  pre- 
vention of  smoke. 

••In  applying  the  bridge  in  a  setting  it  is  placed  upon 
the  top  of  the  usual  brick  bridge,  the  lower  edge  of  the 
fire-plate  .1  being  slightly  below  the  top  of  the  grate- 
bars.  It  can  be  removed  whenever  necessary  by  being 
drawn  out  longitudinally  through  an  opening  in  the  side 
wall,  without  disturbing  any  of  the  brick  work  of  the 
bridge  on  which  it  rests,  or  any  other  part  of  the  setting, 
am!  replaced  in  a  similar  manner.  This  can  be  done  in 
a  very  short  time,  and  without  the  necessity  of  awaiting 
the  cooling  down  of  the  furnaee-and  combustion  cham- 
ber. The  capability  of  ready  removal  ami  replacement 
for  renewal  or  repair  constitutes  an  important  and 
valuable  feat  lire  of  the  improvement  as  compared  with 
the  ordinary  brick  bridge-walls,  or  with  devices  imbed- 
ded therein,  or  in  the  Betting. 

"Its  advantage,  moreover,  in  durability  will  be  appar- 
ent to  the  practical  engineer  and  steam  user,  inasmuch 
as  the  tire-plate  only  is_  exposed  to  the  direct  action  of 
the  fire  :  and,  from  its  material  ami  form  of  construction, 
[a  possessed  of  greater  power  of  resistance  to  the  des- 


156  Combustion  of  coal. 

tractive  influences  exerted  upon  it.  In  the  event  of 
repair  the  entire  bridge  can  be  removed,  a  new  fire-plate 
be  inserted,  and  the  bridge  replaced  in  position,  with 
much  less  labor  and  expense,  and  with  far  greater  expe- 
dition, than  is  practicable  in  the  case  of  a  brick  bridge- 
wall. 

"The  bridge  is  adaptable  to  any  shape  or  size  of 
furnace  used  in  conjunction  with  steam  boilers,  re-heat- 
ing furnaces,  blast  furnaces,  and  tan-bark  ovens,  without 
change  in  the  brick  work  or  setting,  other  than  remov- 
ing the  upper  portion  of  the  brick  bridge-wall,  and 
forming  an  opening  in  the  side  wall  for  the  insertion  of 
the  bridge." 

This  bridge-wall  has  been  adopted  by  the  Hartford 
Steam  Boiler  Inspection  and  Insurance  Company,  in 
their  system  of  boiler  settings,  and  is  said  by  them  to 
give  good  results  in  practice. 

The  admission  of  air  above  or  beyond  the  fuel  is  not 
always  to  be  regarded  as  a  remedy  for  the  low  evapora- 
tive efficiency  of  a  boiler  or  the  low  heating  power  of 
coal  under  all  conditions.  Sometimes  this  admission  of 
air  may  prove  to  be  of  the  greatest  value ;  under  other 
conditions,  it  may  not  be  of  the  slightest  service,  and, 
indeed,  it  may  lower  the  temperature  of  the  furnace  so 
far  below  the  point  of  economy  as  to  prove  an  evil 
instead  of  a  remedy. 

Unfortunately  there  is  no  way  in  which  this  question 
can  be  finally  settled,  except  by  direct  experiment,  and 
this  would  apply  to  one  particular  furnace  only,  and 
perhaps  for  only  one  particular  kind  of  coal,  i.  e.,  either 


Plate  II. 


Fief.  2 


McMURRAY'S  CORRUGATED  IRON  AIR  BRIDGE  WALL. 


EQUIVALENT    EVAPORATION.  157 

anthracite  or  bituminous,  but  not  both.  As  the  subject 
now  stands,  it  amounts  to  little  less  than  a  mere  specu- 
lation to  predict  in  advance  the  performance  of  any 
furnace,  in  so  far  as  perfect  combustion  is  concerned, 
but  in  general  terms  it  may  be  said  that,  if  the  perform- 
ance of  any  boiler  has  an  equivalent  evaporation  of  less 
than  ten  pounds  of  water,  from  and  at  a  temperature  of 
212°  Fahr.  per  pound  of  net  combustible,  there  must 
certainly  be  something  wrong  in  the  construction  of  the 
boiler,  furnace,  or  setting,  which  demands  immediate 
attention. 


CHAPTER  VIII. 

PRODUCTS  OF  COMBUSTION. 

Carbonic  Acid  —  Carbonic  Oxide — Water — Nitrogen  —  Sulphurous 
Oxide — Surplus  Air — Smoke — Products  of  Perfect  Combustion 
Invisible — How  Soot  is  Formed — Smoke-preventives — The  Cor- 
rosive Action  of  Sulphur  on  Boilers — Ashes  and  ("linker — 
Analysis  of  Coal  Ashes — Color  of  Ashes  as  Indicating  the  Pres- 
ence of  Iron  Pyrites  in  Coal — The  Formation  of  Clinkers — The 
Influence  of  Iron  in  the  Coal  on  the  Formation  of  Clinker — 
Apparatus  for  Gas  Analysis. 

The  combustible  elements  in  coal  are  carbon,  hydro- 
gen, and  sulphur,  the  atmosphere  furnishing  the  oxygen 
necessary  to  convert  the  carbon  into  one  of  the  two 
following  products : 

FORMULA.      COMBUSTION.  PRODUCT. 

Carbonic  acid, COj      complete,  incombustible. 

Carbonic  oxide CO       incomplete,       combustible. 

The  hydrogen  unites  with  oxygen  to  form  water 
II,  0,  in  which  the  combustion  is  complete,  and  the  pro- 
duct incombustible. 

The  nitrogen  of  the  air  remaining  in  the  furnace  after 
the  union  of  the  oxygen  with  the  carbon  and  hydrogen, 
is  incombustible,  and  acts  as  a  dilutant  of  the  gases  in  the 
furnace,  having  no  affinity  for  any  of  the  products  of 
combustion. 

The  sulphur  combines  with  oxygen  to  form  sulphur- 
ous oxide  SO..,,  a  colorless  gas,  with  a  suffocating  odor;  it 
is  a  non-supporter  of  combustion,  instantly  extinguish- 


SMOKE.  159 

ing  flame  when  brought  within  its  influence.  Sulphur- 
ous oxide,  in  absorbing  the  vapor  of  water,  changes 
from 

Sulphurous  oxide,  SO.,  to 
Sulphurous  acid,     S02|  H*  0 

As  there  is  almost  always  an  excess  of  air  supplied 
the  furnace,  often  amounting  to  twice  the  quantity 
needed  for  combustion,  this  excess,  also,  becomes  waste 
product,  and  acts  as  a  dilutant  of  the  furnace  gases. 

Smoke  is  regarded  as  a  product  of  incomplete  com- 
bustion. In  its  widest  application  it  is  made  to  include 
all  the  products  of  combustion  issuing  from  the  chim- 
ney. The  use  of  the  word  is  here  restricted  to  the  par- 
ticles of  solid  carbon  mingled  with  the  escaping  gases, 
or,  it  is  the  sooty  portion  only,  of  the  escaping  products. 
If  the  combustion  of  coal  was  perfect  the  escaping  gases 
would  bo  invisible.  Very  few  analyses  of  smoke  are  on 
record,  but  our  knowledge  of  the  composition  of  coal, 
and  of  the  products  of  the  chemical  union  of  oxygen 
with  its  several  constituents,  we  may  easily  conjecture  a 
qualitative  composition  of  the  escaping  gases,  though 
the  precise  quantities  of  each  may  be  unknown. 

Wlicii  a  charge  of  bituminous  coal  is  thrown  upon 
the  fire,  the  effect  of  the  heat  is  to  detach  small  parti- 
cles of  coal  from  the  surfaces  mosl  rapidly  heated;  these 
particles  are  generally  very  small,  and  in  consequence 
weigh  so  little  a-  to  lie  easily  carried  over  tlie  lire  and 
up  the  chimney  by  the  mechanical  agency  of  the  draft 
alone.     These  particles  of  solid  carbon  reflect  light,  and 


160  COMBUSTION   OF    COAL. 

it  is  this  property  which  renders  them  visible.  If  these 
particles  of  carbon  were  not  present,  the  remaining 
products  would  be  invisible.  Whatever  the  quantity  of 
coloring  matter  in  the  smoke  as  seen  escaping  from  the 
chimney,  it  is  to  be  regarded  as  so  much  fuel  irrecover- 
ably lost.  The  solid  carbon  passing  off  in  this  manner 
is  often  a  considerable  quantity,  but  the  actual  percent- 
age is  almost  always  overstated.  Sometimes  furnaces 
are  so  badly  constructed  that  the  chimneys  leading  from 
them  are  almost  constantly  pouring  into  the  atmosphere 
a  volume  of  gases,  which,  to  judge  from  appearances 
merely,  would  seem  to  be  half  carbon,  or,  that  half  the 
coal  fed  into  the  furnace  was  passing  off  uncombined. 

This  mistaken  notion  as  to  the  percentage  of  carbon 
present,  has  been  so  generally  overrated,  that  devices 
for  "  burning  smoke "  have  been  offered  by  the  score, 
often  accompanied  by  the  most  absurd  claims  in  regard 
to  their  efficiency  as  a  "  smoke  consumer,"  and  the  great 
saving  in  coal  to  be  effected  in  the  event  of  their 
adoption. 

What  is  needed  is  not  so  much  a  smoke  consuming 
as  a  smoke  preventing  furnace,  one  which  shall  be  so 
designed  that  any  fuel  rich  in  hydrocarbon,  can  be  com- 
pletely burned  in  the  furnace  proper,  or  within  the 
chamber  containing  the  incandescent  fuel.  This  can  be 
done  only,  by  the  admission  of  sufficient  air  to  convert 
the  carbon  into  carbonic  acid  and  still  maintain  a 
high  temperature  in  the  furnace.  The  quantity  of  air 
required  in  the  combustion  chamber  of  a  furnace  is 
greater  when  a  fresh  charge  of  bituminous  coal  is  thrown 


SMOKE.  161 

upon  the  fire,  than  that  needed  a  few  minutes  afterwards.. 
If  the  high  temperature  of  the  furnace  could  he  main- 
tained at  the  same  time  a  fresh  charge  is  thrown  upon, 
the  fire,  the  carbonic  acid  would  entirely  dissolve  all 
the  sooty  carbon  present  in  the  flame  and  convert  itself 
by  this  additional  carbon  into  carbonic  oxide,  which  may 
then  by  a  proper  supply  of  air  be  re-converted  into  car- 
bonic acid  by  the  addition  of  another  equivalent  o£ 
oxygen. 

Smoke-prevention  in  a  badly  constructed  furnace  is- 
attended  with  great  practical  difficulties;  the  chief  one 
is  the  admission  of  cold  air  over  the  fire  in  a  sufficient 
quantity  to  convert  these  minute  particles  of  carbon 
into  carbonic  acid,  and  at  the  same  time  not  lower  the 
temperature  of  the  furnace  so  as  to  affect  the  steam- 
producing  power  of  the  boiler,  per  pound  of  coal.  In 
admitting  air  above  the  fuel,  unless  it  can  be  supplied 
hot,  it  ma}'  prove  a  worse  evil  than  the  smoke  itself,  by 
lowering  the  temperature  of  the  gases  in  the  furnace  to 
a  point  below  which  ignition  is  insured.  In  stationary 
boiler  furnaces,  in  which  much  smoke  is  given  off',  per- 
haps the  best  thing  to  do  is  to  lengthen  the  grate  by 
carrying  the  bridge-wall  farther  back;  the  limit  to  this 
extension  is  a  six-foot  grate;  in  this  manner  increased 
grate  area  is  obtained,  and  a  slower  rate  of  combus- 
tion. Now,  by  proper  tiring,  tins  may  be  a  means  of 
largely  reducing  the  escape  of  soot  and  carbon.  The 
coal  should  not  be  spread  evenly  over  the  grate,  but 
banked  up  near  the  door,  and  allowed  to  distill  off  the 

gaseous  portions  slowly,  which,  in  passing  over  the  bed 
(12) 


162  COMBUSTION   OF    COAL. 

of  incandescent  fuel,  are  burned;    after  the    charge  of 
fuel  has  lost  most  of  its  volatile  matter  it  may  then  be 
broken  up  and  spread  over  the  grate. 

A  fire-door,  having  perforations,  or  preferably  an  air 
inlet  along  its  lower  edge  only,  may  prove  of  great  ser- 
vice in  admitting  air  where  it  is  most  needed. 

In  cases  where  the  above  is  not  practicable,  a  fan- 
blast  may  be  used  in  connection  with  a  closed  ash-pit, 
and  thus  greatly  intensify  the  action  of  the  furnace;  in 
which  case  the  grate  area  may  be  reduced. 

By  either  of  these  methods  the  quantity  of  smoke 
escaping  may  be  reduced  to  within  very  narrow  limits, 
if  not  entirely  prevented ;  the  latter,  however,  can 
scarcely  be  expected  so  long  as  coal  is  fed  to  the  furnace 
in  large  lumps,  and  in  considerable  quantities,  at  long 
intervals. 

SULPHUR  A  CAUSE  OF  CORROSION  IN  BOILERS. 

There  exists  in  France  a  commission  whose  special 
duty  it  is  to  look  after  boilers,  and  to  try  and  find  out 
the  causes  of  accidents.  A  report  was  made  to  this  com- 
mission after  a  thorough  examination  by  M.  Hanet- 
Clery,  a  mining  engineer-in-chief,  on  the  corrosion  of 
steam  boilers  by  the  action  of  sulphuric  acid.  The  com- 
mission had  its  attention  drawn  to  the  explosion  of  two 
steam  boilers,  one  at  a  colliery  in  the  Nievre,  the  other 
at  the  Ougree  iron  works,  in  Belgium,  and  which  were 
attributed  to  the  destructive  effect  on  the  metal  in  con- 
sequence of  the  presence  of  sulphuric  acid  in  deposits 
left  by  the  smoke  on  certain  parts  of  the  sides  of  the 


SULPHUR  A  CAUSE  OF  CORROSION  IN  BOILERS.     163 

boiler.  Other  facts,  or  supposed  facts,  of  like  import 
appeared,  and  the  subject  was  brought  before  the  scien- 
tific and  industrial  world  in  the  Annates  des  Mines  et  des 
Ponts  et  Chaussees,  the  problem  being  whether,  under 
given  conditions,  the  sulphurous  acid  of  the  smoke  was 
turned  into  sulphuric  acid,  and  the  report  of  M.  Hanet- 
Clery  is  one  of  the  results  (25). 

"As  regards  the  two  accidents  already  referred  to: 
"1.  The  one  which  happened  at  the  colliery  oc- 
curred under  the  following  circumstances  :  The  boiler 
which  burst  was  cylindrical,  the  fire  being  placed  exactly 
beneath,  and  a  superheater,  from  the  cylindrical  boiler 
by  a  brick  arch,  which  nearly  touched  the  upper  part  of 
the  superheater.  The  latter  was  torn  wide  open  in 
front,  to  the  right  of  the  strip  which  covered  a  longi- 
tudinal joint  of  two  plates  of  iron,  and  then  perpendic- 
ularly to  the  end  on  both  sides. 

"The  thickness  of  the  iron  at  the  part  which  gave 
way  first  had  originally  been  twelve  millimeters,  or  half 
an  inch  nearly,  but  it  had  been  reduced  to  1.7  millime- 
ter, and  consequently  totally  incapable  of  supporting 
the  pressure  of  six  kilograms,  under  which  the  boiler 
worked.  The  destruction  of  the  iron  was  all  on  the 
exterior,  and  extended — though  not  equally — over  the 
upper  end  on  the  side  not  exposed.  The  mischief  had 
all  occurred  in  five  years. 

•  M.  Douville,  a  mining  engineer,  attributed  it  to  the 
corrosive  action  of  oxygen  and  sulphurous  acid,  con- 
tained in  the  products  of  combustion  in  the  presence  of 
water  coming  from  a  fissure  in  the  boiler  above,  which, 


164  COMBUSTION    OF    COAL. 

having  traversed  the  brick  vaulting,  fell  on  the  re-heater, 
wetting  the  upper  part,  which  was  relatively  cold,  being 
situated  at  the  extremity  of  the  circuit  of  smoke,  and 
close  to  the  point  where  the  feed- water  arrived,  and  he 
remarked  that  the  water  vapor  contained  in  the  smoke 
was  liable  to  condense  there,  and  the  effect  of  this  con- 
densation might  be  added  to  that  of  the  infiltration,  and 
favor  the  oxidation  of  the  sulphurous  acid  into  sul- 
phuric acid;  the  water  from  the  boiler  concentrating 
itself  chiefly  along  the  edge  of  the  cover-plate  over  the 
joint  of  the  two  plates,  which  prevented  it  descending. 
It  would  thus  moisten  the  deposits  iif  this  part,  which 
the  form  of  the  brick  work  prevented  being  regularly 
cleaned,  and  thus  favored  oxidation  of  the  sulphurous 
acid  in  sulphuric  acid  on  the  surface  of  "the  metal.  M. 
Douville  found  large  scales  of  oxide  of  iron  on  the  cor- 
roded parts,  and  also  sulphur  in  some  form  of  combina- 
tion. 

"2.  The  accident  at  the  Ongree  works  presented 
more  conclusive  evidence;  in  this  case,  sulphuric  acid 
was  actually  found  in  a  free  state,  as  well  as  in  the  form 
of  sulphate  of  iron.  The  following  are  the  circum- 
staiices  of  this  case:  The  boiler  was  horizontal  and 
cylindrical,  with  two  water  tubes  below,  and  it  was 
heated  by  the  flames  of  the  puddling  furnaces.  These 
flames  at  once  enveloped  one  of  the  tubes  and  half  the 
lower  part  of  the  boiler  itself,  and,  making  the  circuit, 
heated  the  other  half  and  second  tube.  The  tube  to  the 
right  of  which  the  flames  debouched  was  torn  open  in 
much  the  same  manner  as  the  superheater  in  the  former 


SULPHUR  A  CAUSE  OF  CORROSION  IN  BOILERS.  165 

case;  the  fracture,  taking  two  courses  perpendicu- 
larly, one  in  the  iron  plate  itself,  the  other  along  a  riv- 
eted seam.  The  thickness  of  the  iron  was  reduced  to 
about  one  millimeter  (one  twenty-fifth  of  an  inch),  at 
the  edffes  of  the  first  rent.  The  corrosion  was  all 
exterior. 

".Two  samples  of  the  soot,  etc.,  left  by  the  smoke  in 
the  parts  destroyed  were  analyzed ;  they  gave  sulphate 
<>f  iron  between  fifty-two  and  fifty-three  per  cent.,  and 
free  sulphuric  acid  in  one  sample  1.42,  and  the  other 
nearly  twelve  per  cent.  Soot  from  other  parts  also  con- 
tained sulphuric  acid,  but  not  enough  to  have  any 
sensible  result  on  the  iron. 

"The  action  is  thus  explained:  the  soot,  etc.,  is 
deposited  during  the  working  of  the  puddling  furnaces 
in  an  entirely  dry  state,  but  when  the  fires  are  put  out, 
the  air,  loaded  with  humidity,  enters  and  converts  the 
soot  into  a  paste;  the  oxidation  of  the  sulphurous  acid 
then  occurs,  and  the  iron  is  in  the  best  condition  to  be 
attacked.  The  corrosive  action  is  thus  going  on  all  the 
time  the  boiler  is  not  in  work,  in  parts  that  could  not. 
be  cleaned  out,  while  no  such  action  occurred  where  the 
soot  had  been  cleared  away. 

"3.  Examples  <>f  exterior  corrosion  by  condensation 
of  steam  suspended  in  the  smoke  on  the  colder  portions 
of  boilers  were  pointed  out  by  M.  Meunier  Dollfus  some 
years  since,  and  published;  one  of  these  cases  was 
observed  at  the  works  of  M.  Charles  Kestner,  at  Thaun. 

"The  works  contained  two  cylindrical  boilers  with 
three  tubes,  and  between  them,  in  t lie  same  brick-work, 


166  COMBUSTION   OF   COAL. 

six  re-heaters  arranged  in  pairs  on  three  stages.  The 
flames  circulated  under  the  three  tubes,  twice  around  the 
boiler  itself,  and  then  in  the  three  stages  of  the  re-heater 
from  above  downwards.  The  feed-water  traversed  in 
the  opposite  direction.  Generally  only  one  of  these 
boilers  was  used  at  a  time,  working  night  and  day,  but 
less  actively  at  night. 

"  In  an  experiment,  when  the  feed- water  arrives  at  a 
temperature  of  68°  Fahr.,  the  water  of  the  first  re-heater 
below  only  marked  86°  Fahr.  on  issuing,  and  that  of  the 
third  re-heater  at  122°  Fahr.  On  the  other  hand,  the 
temperature  of  the  smoke  and  gases  at  the  issue  of  the 
third  re-heater  did  not  exceed  302°  Fahr.  in  the  day 
and  212°  Fahr.  at  night.  At  the  end  of  two  years' 
working,  under  the  above  conditions,  the  re-heaters 
were  already  attacked,  and  at  the  end  of  six  years, 
although  the  iron  was  of  excellent  quality,  they  were  so 
reduced  that  they  had  to  be  replaced.  The  corrosion 
took  place  on  the  colder  portions  of  the  re-heaters,  and 
it  was  found  that  the  first  cause  was  the  sulphurous 
acids  contained  in  the  condensed  steam  deposited  by 
the  smoke,  and  in  the  presence  of  air  and  of  these  acid 
waters,  oxidation  of  the  iron  readily  occurred,  with  the 
subsequent  production  of  sulphate  of  iron. 

"4.  Observations  have  also  been  made  on  this  cause 
of  destruction  of  boilers,  by  M.  Cornut,  Engineer  of  the 
Association  of  the  Proprietors  of  Steam  Apparatus  of 
the  Xorth  of  France,  at  Lille.  He  often  observed 
exterior  corrosions,  which  he  attributed  to  the  action  of 
smoke,  and  which  he  found  absolutely  confined  to  those 


&ULPHUR  A  CAUSE  OF  CORROSION  IN  BOILERS.  167 

parts  of  the  iron  which  were  wetted  by  infiltration  or 
accident. 

"  5.  Resuming  the  facts  stated  above,  the  transform- 
ation of  sulphurous  into  sulphuric  acid,  under  the  action 
of  water,  or  steam  and  air,  in  presence  of  a  metal  is  not 
new.  This  property  of  sulphurous  acid  has  even  been 
employed  practically  in  treating  certain  minerals,  and 
in  purifying  the  neighborhood  of  certain  metallurgical 
establishments.  We  may  mention  as  a  notable  instance, 
the  process  of  M.  Lamine,  for  the  manufacture  of  sul- 
phate of  alumina  at  Ampain,  in  Belgium,  and  the  treat- 
ment of  certain  oxides  of  copper  on  the  banks  of  the 
Rhine.  Such  applications  as  these,  not  of  recent  date, 
should  have  awakened  engineers  to  the  possibility  of 
the  destruction  of  the  iron  boilers  by  a  like  action,  but 
such  was  not  the  case,  and  it  remains  to  be  noted  that  if 
the  fact  is  now  well  known,  the  subject  requires  to  be 
most  carefully  studied  in  all  its  details,  some  of  which 
can  not  fail  to  be  of  practical  importance." 

Conclusion — The  whole  may  be  summed  up  as  fol- 
lows: In  the  matters  deposited  on  the  plates  of  boilers, 
at  a  certain  distance  from  the  fire,  and  which  are  ren- 
dered humid  by  any  accidental  cause,  the  ..sulphurous 
acid  carried  forward  by  the  combustion  gases,  attack 
the  iron  by  the  formation  of  sulphate  of  iron. 

The  attack  may  occur  while  the  boiler  is  heated 
through  an  escape  of  water,  from  the  boiler  itself,  by 
infiltration  through  the  brick  work,  or  by  the  condensa- 
tion of  -team  in   the  flames  and   smoke  in  contact  with 


168  COMBUSTION    OF   COAL. 

iron  plate  relatively  cold.  It  may  also  occur  when  the 
boiler  is  not  in  use,  by  means  of  the  penetration  of  the 
air  into  the  flues. 

The  diverse  origin  of  the  corrosive  action  points  out 
the  nature  of  the  precautious  to  be  taken  to  obviate 
the  destruction,  except  as  applies  to  the  condensation  of 
the  vapors,  on  which  subject  many  arrangements  have 
been  recommended,  but  have  not  yet  obtained  the  sanc- 
tion of  experience. 

The  precautions,  alluded  to  above,  are  only  such  as 
should  be  taken  in  ordinary  practice  for  the  preserva- 
tion of  apparatus;  that  is  to  say,  careful  design  and 
construction,  and  systematic  and  complete  cleansing. 

ASHES  AND  CLINKEK 

Every  variety  of  mineral  fuel  contains  more  or  less 
incombustible  matter  called  ashes.  The  presence  of 
this  incombustible  substance  in  coal  is  due  in  part  to 
the  inorganic  matter  contained  in  the  plants  of  which 
the  coal  is  formed,  and  partly  by  the  earthy  matter  in 
the  drift  of  the  coal  period.  The  percentage  of  ash 
varies  considerably  for  different  coals,  but  it  is  generally 
less  in  the  anthracite  than  in  the  bituminous  varieties. 

Upon  analysis  coal  ashes  are  found  to  consist  princi- 
pally of  silica,  alumina,  lime,  and  oxide  and  bisulphide 
of  iron.  The  nature  and  color  of  ashes  are  greatly 
modified  by  the  proportions  in  which  the  above  sub- 
stances are  united  in  the  composition.  In  the  following 
analysis,  as  in  all  analyses  of  coal  ashes,  silica  and 
alumina  predominate. 


ASHES    AND    CLINKER.  169 


Analysis  of  ashes  of  Pennsylvania  anthracite  coal, 
by  Professor  W.  R.  Johnson : 

Silica 53.60 

Alumina 36.69 

Sesquioxide  of  iron 5.59 

Lime 2.86 

Magnesia 1.08 

Oxide  of  Manganese .19 

100.01 

The  next  analysis  is  from  the  geological  survey  of 
Ohio: 

Bituminous  coal.     Percentage  of  ash,  5.15. 

Silica 58.75 

Alumina 35.30 

Sesquioxide  of  iron 2.09 

Lime 1.20 

Magnesia 0.68 

Potash  and  soda 1.08 

Phosphoric  acid 0.13 

Sulphuric  acid 0.24 

Sulphur,  combined 0.41 

99.88 

An  ordinary  sample  of  block  coal,  from  Clay  county, 
Indiana,  was  analyzed  by  Professor  E.  T.  Cox,  and 
found  to  contain, 

Fixed  carbon 56.50 

(las 32.50 

Water 8.50 

Adi 2.50 

Km. (ill 


170  COMBUSTION   OF    COAL. 

Specific  gravity,  1.285 

Coke:  Not  swollen,  laminated,  lusterless. 

Composition  of  Ash :     Color,  white. 

Iron,  sesquioxide 82 

Alumina 1.20 

Silica,  lime,  magnesia,  etc .48 

2.50 

Of  the  sulphur  present  in  the  coal, 

.947  was  in  combination  with  iron. 
.483  with  other  constituents. 

1.430  per  cent,  of  sulphur  in  the  sample. 

Nearly  every  variety  of  coal  contains  more  or  less 
iron-pyrites ;  this  is  the  probable  source  of  the  oxide  of 
iron  in  the  ashes;  the  greater  part  of  the  sulphur  being 
expelled  by  heat,  its  equivalent  of  oxygen  unites  with 
the  iron,  and  with  which  hydrogen  also  combines,  form- 
ing the  sesquioxide  of  iron  of  the  analysis.  The 
amount  of  oxide  of  iron,  present  in  ashes,  is  one  of 
great  importance,  especially  as  it  unites  with  the  potash, 
soda,  lime  and  silica,  also  present,  to  form  clinker.  The 
presence  of  iron  in  ashes,  when  in  any  considerable 
quantity,  may  be  detected,  without  analysis,  by  the  red 
color  imparted  to  them.  When  the  amount  of  iron  is  very 
small,  or  not  sufficient  to  tinge  the  ashes,  they  are  then 
usually  white;  so  the  terms  red-ash  and  tohite-ash  may 
be  a  sort  of  index  by  which  we  may  judge  of  the  prob- 
able nature  of  the  ashes,  whether  they  will  clinker  in 
the  fire  or  not.  The  intensity  of  the  red  color,  taken 
in  connection  with  the  amount  of  ashes  in  coal,  may 


ASHES    AND    CLINKER.  171 

also  serve  as  an  indication  of  the  proportion  of  sulphur 
existing  in  the  state  of  pyrites. 

The  particular  objection  to  the  combination  and  fusing 
of  the  silica,  lime,  potash,  soda,  etc.,  in  the  ashes  of  the 
coal  into  a  vitreous  mass  is,  that  unless  the  greatest  care 
is  exercised,  it  will  accumulate  upon  the  grate-bars  in 
sufficient  quantity  as  to  exclude  the  passage  of  the  air 
needed  for  combustion,  and  thus  lower  the  temperature 
of  the  furnace. 

These  several  constituents  are  variable  in  their  nature, 
and  by  the  forms  they  take  under  different  intensities  of 
combustion,  much  affect  the  efficiency  of  the  coals  to 
which  they  belong  (23).  Being  differently  fusible  them- 
selves, and  affecting  differently  the  fusion  of  each  other, 
no  two  of  the  earths,  alkalies,  or  metallic  oxides  of  the 
ashes,  but  differ  in  their  agency  when  subjected  to  an 
elevated  heat,  and  their  mutual  reactions  are  moreover 
changed,  as  the  temperatures  are  changed  to  which  they 
are  exposed.  It  hence  arises  that  the  residue  from  many 
coals  melts  to  a  large  extent,  under  no  very  intense  com- 
bustion, into  various  descriptions  of  hard  semi-vitreous 
Blags;  others  yield  a  less  stony  clinker;  and  some  again, 
at  a  far  more  elevated  heat,  result  only  in  a  partially 
agglutinated,  spongy,  open  cinder,  or  even  in  a  pulveru- 
lent or  flaky  ash.  There  are,  perhaps,  no  coals  whose 
ashes,  when  exposed  to  the  extremest  heats  procurable 
by  artificial  Musts,  will  not  soften  to  a  cohering  cinder, 
or  cv.n  melt  in  pari  into  a  stony  clinker;  but  as  the 
tendencies  to  these  several  degrees  of  fusion  are  very 
various,  i1  [troves  to  be  a  distinction   affecting  the  prac- 


172  COMBUSTION   OF    COAL. 

tical  value  of  coals,  which  is  of  the  utmost  importance. 
In  domestic  consumption,  where  the  heat  of  combustion 
is  comparatively  moderate,  the  quantity  rather  than  the 
quality  or  fusibility  of  the  ashes  is  the  point  of  greatest 
consideration ;  but  where  an  excessive  and  melting  heat 
is  required,  as  in  many  modes  of  generating  steam,  the 
practicability  of  employing  a  coal  at  all  will  oftentimes 
be  determined  by  this  one  quality  of  clinkering  of  the 
ashes.  In  all  such  circumstances,  those  coals  are  best 
the  ashes  of  which  are  of  a  nearly  pure  white,  and 
which,  with  large  amounts  of  silica  and  alumina  in  their 
composition,  contain  little  or  no  alkali,  nor  any  lime, 
nor  oxide  of  iron.  Of  this  character,  are  the  earthy 
residue  of  the  best  white-ash  anthracites,  of  Pennsyl- 
vania, and,  in  an  eminent  degree,  the  ashes  of  some  of 
the  semi-anthracites. 

In  general,  it  requires  a  high  temperature  to  fuse 
these  ingredients  when  taken  by  themselves,  but  the 
presence  of  the  oxide  of  iron  tends  to  lower  the  point 
of  fusion,  and  thus  increases  the  difficulty. 

The  grate  bars  recommended  for  any  coal,  the  ashes 
of  which  are  liable  to  clinker,  are  any  of  those  forms 
which  may,  while  in  position  and  in  use,  be  either 
shaken,  tilted,  or  revolved  without  injuriously  breaking 
up  the  fire. 

APPARATUS  FOB  GAS  ANALYSIS  (19). 

As  a  rule,  gaseous  agents  hold  a  very  important 
position  in  technical  chemistry,  whether  atmospheric, air 
be  employed  in  ordinary  cases,  or  under  circumstances 


APPARATUS  FOR  GAS  ANALYSIS.  173 

in  which  the  employment  of  other  gases  is  desirable  for 
chemical  analysis.  In  most  of  the  latter  cases  special 
apparatus  is  desirable  for  the  production  of  such  gases. 
If  we  take  metallurgical  analysis,  for  example,  as  a 
branch  of  technical  chemistry,  we  shall  frequently  find 
that  remarkable  and  crucial  differences  occur  according' 
to  the  gas  employed.  The  question  of  their  quantity 
frequently  becomes  of  importance  in  regard  to  first  indi- 
cations for  qualitative  and  quantitative  analysis,  as  an 
instance  of  which  may  be  mentioned  the  free  combus- 
tion of  any  form  of  carbon,  supposing  the  amount  of 
air  present  to  have  been  entirely  utilized,  taking  at  the 
same  time  the  relation  of  the  weight  of  air  to  that  of 
consumed  carbon.  But  in  all  such  cases  great  uncer- 
tainty  exists  in  the  exact  estimation  of  such  relations. 

Despite  the  advantage  of  its  study,  that  of  gaseous 
analysis  has  scarcely  yet  found  its  proper  position  in 
technical  chemistry,  although  the  latter  branch  of  sci- 
ence has  of  late  made  very  rapid  strides.  The  reason  of 
this  may  lie  partly  explained  on  the  ground  that  there 
is  much  difficulty  in  manipulating  with  all  gases,  result- 
ing from  the  delicacy  of  the  apparatus  employed  in  the 
laboratory,  and  the  usual   slowness  of  such  operations. 

Although  comparatively  few  gases  are  met  with  in 
technological  operations,  yet  their  action  predominates 
over  almosl  any  other  agent,  and  consequently  it  is 
desirable  to  arrange  such  an  apparatus  more  simple  than 
those  usually  employed  in  laboratories,  without  the  use 
of  *the  pneumatic  trough  of  water  or  mercury  (both 
frequently  inconvenient),  nor  requiring  barometrical  or 


174 


COMBUSTION   OF    COAL. 


thermometric  corrections  hitherto  considered  indispen- 
sable. It  is  desirable,  in  fact,  to  present  such  an 
arrangement  as  shall  be  readily  available  for  the  use  of 
ordinary  intelligent  workmen,  so  as  to  furnish  not  only 
ready  but  comparatively  trustworthy  indications. 

For  the  purpose  just  referred  to,  M.  De  H.  Orsat,  of 
Paris,  has  suggested  the  apparatus  here  illustrated. 


Figure  4. 


"The  apparatus  consists  essentially  as  a  graduated 
pipe,  A  _B,  placed  in  a  receiver  filled  with  water, 
intended  to  preserve  a  constant  temperature,  a  most 
important  point  in  gas  analysis.  This  graduated  tube 
communicates  at  A  with  a  horizontal  capillary  tube,  fur- 
nished with  a  stop-cock,  C,  through  which  the  gas 
passes  into  the  measuring  apparatus.  The  lower  por- 
tion of  the  measuring  arrangement  is  connected  by  an 
India  rubber  tube,  0,  to  a  gas  jar,  i>,  by  means  of  an 
opening  at  the  bottom;  this  jar  being  partly  filled  with 
water,  the  water  in  this  jar  may  be  lowered  by  sucking 


APPARATUS  FOR  GAS  ANALYSIS.  175 

out,  or  raised  by  blowing  into  it.  The  horizontal  tube 
is  connected  by  two  branches  furnished  with  two  stop- 
cocks, G  and  if,  with  two  bell-glasses  placed  in  the 
eprouvettes,  E  and  F,  which  contain  the  liquids 
intended  to  absorb  the  gases  under  examination  or  use. 
The  first  eprouvette,  JE,  contains  a  solution  of  caustic 
potass.  The  bell-glass  is  entirely  filled  with  small  tubes 
of  glass,  open  at  both  ends,  and  intended  by  capillary 
and  other  action  to  facilitate,  as  far  as  possible,  the  rapid 
absorption  of  the  gas  in  the  bell-glasses. 

"The  second  eprouvette,  F,  contains  an  ammoniacal 
solution  of  chloride  of  ammonium  (sal-ammoniac).  The 
interior  of  the  second  bell-glass  is  filled  with  metal  foil, 
consisting  of  copper,  in  repeated  coils,  so  that  at  the 
same  time  oxygen  shall  be  absorbed,  oxide  of  carbon, 
in  the  presence  of  the  saline  solution,  by  chemical  action, 
combining  with  the  physical  action  of  the  tubes  in  the 
first  eprouvette. 

"For  the  sake  of  safety,  a  fourth  stop-cock  allows 
the  escape  of  gas,  which  would  otherwise  remain  in  the 
apparatus.  If  the  .tube  N,  which  brings  the  gas,  has 
great  length,  it  is  easily  cleaned  by  the  arrangement, 
marked  A'  L  JI,  by  water.  It  is  sufficient  to  send  a  few 
decimeters*  of  water  by  the  tube,  K  M,  to  produce  an 
lip-draft  in  L,  to  act  as  a  balance  to  the  gas  in  X.  A 
litre  of  water,  or  say,  a  quart,  English,  is  sufficient  to 
effed  this  in  a  tube  of  four  millemeters  (0.15  in.)  in 
diameter.  13y  connections  with  the  tube  JV^  by  India 
rubber  piping,  any  apparatus  employed  in  gas  analysis 

A  ili'i  1 1 1 1 1 •  t <_•  r  =  3.94  incli'-. 


176  COMBUSTION   OF    COAL. 

may  be  employed,  and  by  very  simple  arrangements  the 
outer  apparatus  may  be  applied  for  any  of  the  objects 
hereafter  named. 

"The  explanation  of  the  use  of  the  apparatus  will 
be  better  understood  by  the  following  remarks : 

"The  first  bell-glass  receives  gases  absorbable  by 
means  of  a  solution  of  caustic  potass;  the  second  receives 
those  which,  being  not  absorbed  by  the  first,  are  absorb- 
able by  means  of  a  solution  of  copper.  For  example,  in 
the  ordinary  combustion  analysis,  the  first  absorbs  car- 
bonic acid,  and  the  second  oxygen  and  carbonic  oxide. 

"  In  the  ordinary  state  of  combustion,  both  of  these 
gases  are  given  off,  and  some  inconvenience  might  be 
supposed  to  arise  from  the  fact,  but  the  difficulty  is 
more  apparent  than  real. 

"  They  are  easily  separated  on  account  of  their 
chemical  individuality. 

"In  certain  cases,  it  happens  that  carbonic  oxide 
may  remain  with  oxygen,  but  even  in  this  case 
an  approximative  result  of  their  proportions  may  be 
obtained,  when  the  combustible  matter  does  not  afford 
free  oxygen  nor  hydrocarbons.  Practically,  the  oxygen 
afforded  by  the  atmosphere  does  not  change  its  volume 
by  aiding  to  produce  carbonic  acid,  while  its  volume  is 
doubled  by  producing  carbonic  oxide.  It,  therefore, 
becomes  a  simple  question  of  calculation  to  determine 
the  nitrogen  in  the  measured  tube,  and  any  other  deter- 
mination depending  on  measurement  in  the  absence  of 
absorption. 

"In  certain  cases  the  addition  of  a  third  bell-glass 
would  be  desirable,  especially  in  the  event  of  the  respect- 


APPARATUS    FOR    GAS    ANALYSIS.  177. 

ive  presence  of  oxygen  and  carbonic  oxide  requiring  to^ 
be  determined.  The  third  glass  should  then  be  sup- 
plied with  pyrogallate  of  potash,  or  stick  of  phospho- 
rus. Sulphurous  acid  may  also  be  determined  by  the 
apparatus,  also  hydrosulphuric  acid  (sulphureted  hydro- 
gen), and  chlorine.  In  special  cases  the  apparatus  might 
be  employed  for  estimating  gases  -which  present  them- 
selves in  a  separate  form:  sulphurous  acid,  for  example,. 
in  the  presence  of  carbonic  acid,  may  be  estimated  by  * 
solution  of  potass  in  sulphuric  acid  (and  water),  or  by 
the  permanganate  of  potash.  When  gases  very  solu- 
ble in  water  are  to  be  examined,  as,  for  example,  sul- 
phurous acid,  there  should  be  a  substitute  of  glycerine 
in  the  bottle  or  flask,  D,  in  place  of  water.*' 

The  value  of  this  apparatus  largely  rests  on  the  fact 
that  it  may  be  placed  in  the  hands  of  an  ordinary  work- 
man for  qualitative  analysis  to  control  his  operations. 
At  the  same  time  its  indication  may  be  controlled  by 
very  simple  arrangements,  so  that  the  manager  may 
notice  the  indications  afforded  by  each  apparatus,  with- 
out the  knowledge  of  those  using  it.  It  is  applicable 
to  a  large  variety  of  purposes,  as,  lor  example,  the  esti- 
mation of  the  gaseous  products  of  reverbatory  furnaces, 
puddling  furnaces,  the  Bessemer,  and  Danks  arrange- 
ments for  dealing  with  pig-iron,  the  production  of  car- 
bonic  acid  in  lime-burning,  sugar  works;  the  manufac- 
ture of  alkaline  carbonates,  wine,  beer,  and  vinegar 
production,  with  an  immense  variety  of  technical  and 
other  purposes. 
(13) 


CHAPTEE    IX. 

THERMAL  POWER  OF  FUELS. 

Heat  Developed  by  Chemical  Action  —  Favre  and  Silberman' s 
Apparatus  —  Units  of  Heat  Evolved  by  Elemental  Combus- 
tion— Heat  Developed  by  the  Combustion  of  Coal — Allotropic 
States  of  Carbon  —  Proximate  Constitution  of  Coal  —  Experi- 
ments of  Scheurer-Kestner  and  Meunier-Dollfus  on  the 
Calorific  Power  of  Coal — Thompson's  Calorimeter — Manner  of 
Conducting  Experiments— Evaporative  Power  of  Coal — Object 
in  Reducing  Evaporation  to,  from  and  at  212°  Fahr. 

The  total  heat  of  any  combustible  may  be  calculated, 
if  its  proximate  or  elementary  analysis  is  known,  by 
means  of  data  analogous  to  that  furnished  by  Favre  and 
Silberman,  or  it  may  be  determined  by  means  of  a 
calorimeter,  similar  to  that  of  Thompson,  described  in 
this  chapter. 

HEAT  DEVELOPED  BY  CHEMICAL  ACTION. 

The  apparatus  used  by  Favre  and  Silberman  for 
measuring  the  heat  evolved  by  the  combustion  of  vari- 
ous substances  in  oxygen  gas  is  represented,  with  the 
omission  of  minor  details  (13),  in  figure  5.  C  is  a  ves- 
sel of  gilt  brass  plate,  immersed  in  a  water-calorimeter, 
A  A,  of  silvered  copper  plate,  and  the  latter  is  enclosed 
in  an  outer  vessel,  B  B,  the  space  between  A  and  B 
being  filled  with  swan-down,  to  prevent  the  escape  of 
heat  from  the  water  in  A.  The  vessels  A  and  B  are 
closed  with  lids  having  apertures  for  the  insertion  of 
tubes   and   thermometers.     The    combustions   are   per- 


HEAT    DEVELOPED    BY    CHEMICAL    ACTION. 


179 


formed  in  the  vessel  C,  into  which  oxygen  is  introduced 
through  the  tube,  c  d,  and  the  gaseous  products  of  the 
combustion  escape  by  the  tube,  e  f  g  h,  the  lower  part  of 
which  is  bent  into  numerous  coils,  to  facilitate,  as  much 
as  possible,  the  transmission  of  the  heat  of  these  gases 
to  the  water  in  the  calorime- 
ter. The  extremity,  h,  of  this 
tube  is  connected  with  a  gaso- 
meter, or  with  an  absorbing 
apparatus.  To  insure  uniform- 
ity of  temperature  in  the  wa- 
ter, a  Hat  ring  of  metal,  i  i,  is 
moved  up  and  down  by  means 
of  the  rod,  K  i.  Combustible 
gases  were  introduced  into  the 
vessel  C,  by  means  of  tine  tubes, 
the  gas  being  previously  set  on 
fire  at  the  aperture.  Solid 
bodies  were  attached  to  fine  platinum  wires  suspended 
from  the  lid  of  the  calorimeter;  the  liquids  were  burned 
in  small  capsules,  or  in  lamps  with  asbestos  wicks: 
charcoal  was  disposed  in  a  layer  on  a  sieve-formed  bot- 
tom, through  the  openings  of  which  the  oxygen  had 
access  to  it.  The  heat  evolved  was  measured  by  the  rise 
of  temperature  of  the  known  quantity  of  water  in  the 
calorimeter. 


180 


COMBUSTION    OF    COAL. 


Table  XIX. 

Showing  the  Total  Quantities  of  Heat  Evolved  by  the  complete 
Combustion  of  oxe  pound  of  Combustible  with  Oxygen;  adapted 
from  the  Results  Obtained  by  Favre  axd  Silbebhan.    The  unit 

of  weight  ix  this  table  beixg  oxe  pol'xd,  axd  the  unit  of  tem- 
PERATURE oxe  degree  Fahr.  (from  39°  to  40°). 


SUBSTANCE. 


FORMULA. 


UXITS  OF  HEAT 


Hydrogen 

Carbonic  oxide 

Marsh  gas 

defiant  gas 

LIQUIDS. 

Oil  of  turpentine 

Alcohol 

Spermaceti  (solid) 

Sulphate  of  carbon 

SOLIDS. 

Carbon  (wood  charcoal) 

Gas  coke  

Graphite  from  blast  furnace; 

Native  Graphite 

Sulphur   (native) 


H 
CO 
CH* 
C2H4 

CloII]6 

C2HsO 
QbHmO* 

cs, 

c 


Phosphorus  (observed  by  An 
drews) , 


H20 
C0a 

CO,  &  H2  0 
C02  &  H2  0 

C02*H20 

C02&H20 
C02&H20 
C02  &  S02 

(CO 

1co2 


so2 

P205 


62,032 

4,325 

23,513 

21,343 

19,533 

12,931 

18,616 

6,122 

4,451 
14,544 

14,485 

13,972 

14,035 

4,048 

10,715 


HEAT  DEVELOPED  BY  THE  COMBUSTION  OF  COAL. 

This  may  "be  determined  theoretically  by  taking  the 
units  of  heat  evolved  by  each  element  in  the  coal  separ- 


HEAT  DEVELOPED  BY  THE  COMBUSTION  OF  COAL.        181 

ately — allowing  certain  deductions — and  adding  them 
together.  This  requires  then,  an  elementary  analysis  to 
begin  with.  Assuming,  for  example,  that  a  certain 
sample  of  coal,  weighing  one  pound,  is  analyzed,  and  is 
found  to  contain, 

Carbon 81 

Hydrogen 05 

Oxygen 04 

Nitrogen,  ash,  etc 10 

1.00 

and  that  the  sulphur  and  other  impurities  in  the  coal 
be  disregarded,  we  proceed  to  estimate  its  calorific 
power  in  this  way: 

UNITS.  PER  CENT. 

Carbon 14,500     X     .81  =  11,745 

units  of  heat  in  the  carbon. 

Since  oxygen  and  hydrogen  unite  to  form  water,  the 
whole  of  the  oxygen  must  be  deducted,  together  with  its 
equivalent  of  hydrogen,  before  we  can  determine  the 
calorific  power  of  the  latter,  for  the  available  hydrogen 
in  the  coal  is  only  that  above  the  quantity  required  to 
unite  with  oxygen,  as  stated  above. 

Oxygen  unites  with  -i-  of  its  own  weight  of  hydrogen 
to  form  water;  and, 

i°f  ToF  =  soo- =  -005 

pound  of  hydrogen  neutralized  by  the  presence  of 
oxygen  in  the  coal,  leaving 

."5  —  .005  =  .  015 


182  COMBUSTION   OF    COAL. 

pound  of  available  hydrogen ;  then,  proceeding  as  before : 

UNITS.  PER  CENT. 

Hydrogen 62,032  X  .045=   2,791.     units. 

adding  the 

Carbon 14,500  X  .81    =11,745.     units. 

Total 14,536. 

units  of  heat  in  one  pound  of  coal  of  the  composition 
assumed. 

This  is  called  the  theoretical  calorific  power  of  coal. 

The  nitrogen  and  ash  being  inert,  are  simply  dilut- 
ants,  and  no  account  is  taken  of  them. 

This  appears,  at  first  sight,  a  very  simple  and  easy 
method  of  determining  the  calorific  power  of  coal,  but 
it  is  open  to  serious  objections;  one  is,  the  elementary 
analysis  demanded  as  a  starting  point;  another,  is  the 
uncertain  value  of  carbon. 

The  following  table  is  compiled  from  the  researches 
of  Favre  and  Silberman 

Table  XX. 


VARIETIES  OF   CARBON. 


Diamond 

Graphite — artificial 

Graphite — native 

Carbon  from  gas-retorts . 
Charcoal  from  wood 


UNITS  OF 
HEAT. 


13,986 
13,972 
14,035 
14,485 
14,544 


HEAT  DEVELOPED  BY  THE  COMBUSTION  OF  COAL.         183 

These  substances,  it  may  be  remarked,  are  practically 
elemental,  yet,  the  difference  between  the  two  extremes 
are  live  hundred  and  fifty-eight  heat  units. 

How  much  of  this  difference  is  due  to  the  allotropic 
condition  of  the  carbon  is  not  easily  stated ;  it  is  possible, 
and  altogether  probable  that  it  has  much  to  do  with  it. 

It  might  be  said  that  as  diamonds,  graphite,  and  gas 
carbon  are  not  employed  as  fuel,  it  is  of  little  conse- 
quence what  difference  there  may  be  between  them. 
This  would  appear  to  the  superficial  observer  as  a 
"practical"  truth,  but  it  is  not  so.  It  must  be  remem- 
bered these  are  not  compounds  of  carbon,  but  pure  car- 
bon. If  the  theoretical  power  of  carbon  is  an  uncertain 
quantity,  then,  a  guess  is  as  good  as  a  calculation. 

The  various  kinds  of  coal  found  in  this  country, 
passing  through  an  innumerable  series  of  gradations, 
from  the  least  cohesive  of  the  bituminous  varieties,  to 
the  hard  crystalline  Lehigh  anthracite,  adds  emphasis  to 
the  question  instead  of  waiving  it. 

Assuming  the  calorific  power  of  coke  to  be  known, 
it  is  desirable  to  know  whether  the  volatile  portion  of 
the  coal  yields  the  calorific  power  ascribed  to  it  by 
calculating  t]ie  elementa  separately,  and  adding  them 
together;  also,  whether  the  sum  of  the  heat  units  of 
the  coke  and  volatile  matter  is  more  or  less  than  the 
units  of  heat  given  off  by  the  coal  during  the  actual 
burning.  Various  calorimeters  have  been  devised  to 
ascertain,  if  possible,  a  dose  approximation  to  the 
actual  calorific  power  of  any  given  sample  of  coal  with- 
out undergoing  any  analysis  whatever. 


184  COMBUSTION    OF    COAL. 

This  seems  all  the  more  desirable  as  the  proximate 
constitution  of  coal  is  win  illy  unknown  (20);  we  are 
ignorant  whether  force  is  liberated  or  absorbed  during 
the  decomposition — previously  to,  or  at,  the  moment  of 
combustion — of  the  various  compounds  of  carbon, 
hydrogen  and  oxygen,  of  which  the  organic  part  of  coal 
must  be  composed.  Again,  the  hydrogen  and  oxygen 
are  present  in  the  solid  state,  and  we  are  unable  to 
determine  what  amount  of  force  may  be  absorbed  dur- 
ing their  conversion  into  the  gaseous  state. 

EXPERIMENTS  OX  THE  CALORIFIC  POWER  OF  COAL. 

M.  M.  Scheurer-Kestner  and  Charles  Meunier-Doll- 

fus,  have,  within  a  few  years  past,  made  a  special  study 
of  different  coals  with  reference  to  their  calorific  power, 
making  use  of  a  modified  form  of  the  Favre  and  Silber- 
man  calorimeter,  described  on  page  179  in  this  volume; 
the  modifications  were  such  that  the  carbonic  acid  pro- 
duced on  combustion  was  cooled  with  great  rapidity, 
whereby  the  quantity  of  carbonic  oxide  formed  was 
much  reduced.  It  has  not  been  found  possible  to  pre- 
vent the  formation  of  some  carbonic  oxide  during  the 
combustion  of  carbon,  even  under  the  most  favorable 
conditions,  but  the  amount  produced  in  each  experiment 
can  be  accurately  determined  by  passing  the  products  of 
combustion  first  through  a  solution  of  potash,  which 
absorbs  the  carbonic  acid,  and  afterward  through  a  tube 
containing  black  oxide  of  copper  heated  to  redness. 
By  this  means  carbonic  oxide  can  be  converted  into  car- 


HEAT  DEVELOPED  BY  THE  COMBUSTION  OF  COAL.         185 

bonie  acid,  which  may  he  collected  in  a  solution  of  pot- 
ash and  weighed. 

For  the  sake  of  comparing  the  experimental  with 
the  theoretical  values  of  the  coals  as  deduced  from  their 
composition  in  the  manner  before  described,  they 
reduced  their  experimental  results,  and  calculated  them 
as  though  the  coals  had  consisted  wholly  of  the  organic 
constituents,  excluding  the  ash  and  the  hygroscopic 
water.  They  made  corrections  for  the  carbon,  which,  in 
their  experiments  in  the  calorimeter,  was  retained  in  the 
ash.  and  also  for  the  hydrogen  and  carbonic  oxide  which 
escaped  combustion ;  but  they  appear  to  have  taken  no 
account  of  the  sulphur  in  the  state  of  sulphide,  which 
all  coal  contains,  and  which  would,  in  greater  or  less 
degree,  according  to  its  quantity,  add  to  the  amount  of 
heat  produced  in  the  calorimeter. 


186 


COMBUSTION    OF    COAL. 


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HEAT  DEVELOPED  BY  THE  COMBUSTION  OF  COAL. 


187 


From  an  inspection  of  the  table,  it  will  be  seen,  that 

in  every  case  the  experimental  calorific  power  of  the 

coal  considerably  exceeds  the  calculated  result,  and  that 

coals  with  nearly  the  same  percentage  composition,  so 

far  as  regards  organic  constituents,  may  differ  widely  in 

calorific  power. 

Table  XXII. 

Showing  the  Experimental   Calorific  Power  of  Different  Coals 

AND    LlGN'ITES   AS    OBSERVED  BY  ScHEURER-KeSTXER   AXD    MeUXIER- 
DOLLFUS. 


combustible. 


COAL. 

Bonchamp,  three  samples 

Saarhruck,  seven  samples 

Creusot,  four  samples- 

Blanzy — Monteeau 

Blanzy — Anthraeitic 

Anjrin 

IV  n  a  in 

English— Bwlf 

Bnglish— Powell-Duffryn 

lin  — -irtii  QroacbefsdJ  Anthracite 
Bassian-  -Miouchi,  Bituminous.... 
I . i < — i  ii  —  f    iloubofs  i  i,  flaming 

l.l'.NI  1  I  s. 

blea 

Bohemia,  Bituminous 

Buselan,  Toula 

Lignite,  passing  to  (oaaU  w I 

F>i>>ii  irood,  passing  to  lignite 


GASEOUS  ELEMENTS. 

i 

o 

(8 
H 
< 

o 

a 

i. 
*     g 

£  z  K 

o     x 

PER 
CENT. 

88.59 
81.10 
90.60 
78.58 
87.02 
34.46 
83.94 
91.08 
92.49 
96.66 
91.46 
82.67 

72.98 
76.58 
7:;. 72 
96.61 
67.60 

PER 
CENT. 

4.69 
4.75 
4.10 
5.23 
4.72 
4.21 
4.43 
3.83 
4.04 
1.35 
4.50 
5.07 

4.04 
8.27 
6.09 
179 
4.66 

PER 
CENT. 

6.72 
14.15 

5.30 
16.19 

8.26 
11.32 
11.63 

5.09 

3.47 

1.99. 

4.05 
12.20 

22.98 
16.16 

20.19 
28.77 
87.86 

© '- 1.  'A 

0  o  > 

s.  „  a  « 

o  g  a  g 

x 


UNITS. 

16,416 
15,320 
16,994 
14,986 
16,400 
16,663 
16,290 
15,804 
16,108 
14,866 
15,651 
14,43S 

11,670 
14,268 

13,837 
11,111 
11,360 


188 


COMBUSTION    OF    COAL. 


The  fuel  is  assumed  to  be  dry  and  pure — without 
any  ash. 

THOMPSON'S  CALORIMETER. 

The  object  of  this  instrument  is  to  give  approxi- 
mately, by  means  of  a  simple  experiment,  the  theoretical 
evaporative  power  of  any  fuel  submitted  to  investiga- 
tion (20). 

"  It  consists  of  a  glass  cylinder,  A, 
closed  at  the  lower  end  only,  to  con- 
tain a  given  weight  of  water. 

"B  is  a  cylindrical  copper  vessel, 
called  the  condenser,  closed  at  one  end 
with  a  copper  cover,  in  which  is  fixed 
a  metal  tube  C,  communicating  with 
the  interior  of  the  vessel  B,  and  fitted 
at  its  upper  extremity  with  a  stop- 
cock. The  other  end  of  B  is  open, 
and  it  is  perforated  near  the  open  end 
by  a  series  of  holes,  b  b. 

"D  is  a  metal  base  upon  which  B 
is  fixed  by  means  of  three  springs, 
which  are  attached  to  _D,  and  press 
against  the  internal  surface  of  B,  but 
which  are  omitted  from  the  wood  cut 
for  the  sake  of  clearness.  A  series  of 
holes  is  arranged  round  the  circum- 
ference of  _D  to  facilitate  raising  the 
apparatus  through  the  water. 

"JE  is  a  copper  cylinder,  called  the  furnace,  closed  at 
the  lower  end  only,  which  fits  into  a  metal  ring  or  seat 
on  the  center  of  D. 


Figure  6. 
Scale  one-fourth  full  size. 


THOMPSON  S    CALORIMETER.  189 

"  The  manner  in  which  results  are  obtained  is  as 
follows :  A  known  weight  of  the  fuel  is  burnt  by  means 
of  chlorate  of  potash  and  nitre  at  the  bottom  of  a  vessel 
containing  a  known  weight  of  water ;  the  heat  pro- 
duced by  the  combustion  of  the  fuel  is  communicated 
to  the  water,  and  from  the  rise  in  temperature  of  the 
latter  is  calculated  the  number  of  parts  of  water  which 
the  combustion  of  one  part  of  the  fuel  will  raise  one 
degree  in  temperature:  this  number  being  divided  by 
the  latent  heat  of  steam  (537  or  967  units,  according 
as  the  centigrade  or  Fahrenheit  scale  is  employed), 
gives  the  evaporative  power  of  the  fuel,  i.  e.,  the  num- 
ber of  pounds  of  water  (supposed  to  pre-exist  at  the 
boiling  point)  which  one  pound  of  the  fuel  is  theoreti- 
cally capable  of  evaporating. 

"In  the  instrument,  as  constructed  by  the  manufac- 
turer, it  is  intended  that  thirty  grains  of  the  fuel  should 
be  burnt,  and  that  29,010  grains  (or  nine  hundred  and 
thirty-seven  times  this  weight)  of  water  should  be 
employed;  hence  the  rise  in  the  temperature  of  the 
water,  expressed  in  degress  Fahrenheit,  is  equal  to  the 
Dumber  of  pounds  of  water  which  one  pound  of  the 
fuel  theoretically  will  evaporate;  but  ten  per  cent,  is 
directed  to  be  added  to  this  number,  as  a  correction  for 
the  quantity  of  heal  absorbed  by  the  apparatus  itself, 
and  consequently  not  expended  in  raising  the  tempera- 
ture of  the  water. 

"  In  addition,  the  gaseous  products  of  combustion 
generally  escape  from  the  surface  of  the  water  whilst 
sensibly  warm.     Whether  this  loss  of  heat  is  covered  by 


190  COMBUSTION    OF    COAL. 

the  above  correction,  I  am  unable  to  state;  that  it  is 
not  unimportant,  has  been  proved,  in  my  laboratory,  by 
enclosing  the  lower  part  of  the  condenser  within  a  large 
metallic  cylinder,  perforated  all  over  with  small  holes, 
so  that  the  escape  of  gases  from  the  water  was  retarded 
when  the  experimental  results  obtained  were  notably 
higher.  Thus,  in  comparative  experiments  upon  a 
"Welsh  steam  coal,  it  was  found  that  its  theoretical 
evaporative  power  was  raised  from  14.41  to  14.96  pounds 
of  water,  by  enclosing  the  condenser  in  the  manner 
described.  The  colder  the  water,  the  •  smaller  will  be 
this  loss  of  heat,  owing  to  the.  gases  being  more 
thoroughly  cooled. 

"The  experiment  is  conducted  in  the  following  man- 
ner: Thirty  grains  of  finely-powdered  fuel  is  intimately 
mixed  with  from  ten  to  twelve  times  its  weight  of  a 
perfectly  dry  mixture  of  three  parts  of  chlorate  of 
potash  and  one  part  of  nitre;  the  resulting  mixture, 
which,  for  the  sake  of  distinction,  may  be  called  the 
fuel-mixture,  is  introduced  into  the  furnace,  E,  and  care- 
fully pressed  or  shaken  down.  The  end  of  a  slow  fuse, 
about  half  an  inch  long,  is  next  inserted  in  a  small  hole 
made  in  the  top  of  the  fuel-mixture,  and  is  fixed  there 
by  pressing  the  latter  around  it;  the  furnace  is  then 
placed  in  its  seat  on  the  metal  base,  Z>,  the  fuse  lighted, 
and  the  condenser,  _B,  with  its  stop-cock  shut,  fixed 
over  the  furnace. 

"The  cylinder,  A,  is  previously  charged  with  29,010 
grains  of  water,  the  temperature  of  which  must  be 
recorded,  and  the  apparatus  is  now  quickly  submerged 


EYAPOEATIYE    POWER    OF    COAL.  191 

in  it.  The  fuse  ignites  the  fuel-mixture,  and  when  the 
combustion  is  finished  (indicated  by  the  cessation  of  the 
bubbles  of  gas,  produced  by  the  combustion,  which  rise 
through  the  water),  the  stop-cock  is  opened,  and  the 
water  enters  the  condenser  by  the  holes,  bb. 

"By  moving  the  condenser  up  and  down,  the  water 
is  thoroughly  mixed  and  acquires  a  uniform  temperature, 
which  is  then  recorded.  By  adding  ten  per  cent,  to  the 
number  of  decrees  Fahr.  which  the  water  has  risen  in 
temperature,  the  theoretical  evaporative  power  of  the 
coal  is  at  once  approximately  determined. 

"  The  furnace  shown  in  figure  6  is  intended  to  be 
used  when  bituminous  coals  are  to  be  operated  upon ; 
but  in  experimenting  on  coke,  anthracite  and  other 
difficult  combustible  fuels,  a  wider  and  shorter  furnace 
is  preferred,  and  the  fuel  mixture  should  not  be  pressed 
down." 

Evaporative  Power  of  Coal — By  this  is  meant  the 
number  of  pounds  of  water,  which,  under  certain  condi- 
tions, are  capable  of  being  evaporated  per  pound  of 
coal.  It  is  essential  to  the  obtaining  of  accurate  results, 
that  the  temperature  of  the  feed  water  and  the  tempera- 
ture of  evaporation  should  both  be  ascertained,  and  the 
total  heat  per  pound  of  water  computed.  That  total 
heat  being  divided  by  966,  the  latent  heal  of  evapora- 
tion of  a  poun^l  of  water  at  212°,  gives  a  multiplier,  by 
wh'nh  the  weight  of  water  actually  evaporated  by  cadi 
pound  of  fuel  is  to  be  multiplied,  to  reduce  it  to  the 
ctjiilrnlait  evaporation  from  and  at  '1V1° ;  that  is,  the  weight 


192  COMBUSTION    OF    COAL. 

of  water  which  would  have  been  evaporated  by  each  pound  of 
fuel,  had  the  water  been  both  supplied  dind  evaporated  at 
the  boiling  point  corresponding  to  the  mean  atmospheric 
pressure. 

The  weight  of  water  so  calculated  is  called  the 
evaporative  power  of  the  fuel. 

The  object  of  reducing  evaporative  results  in  prac- 
tice to  equivalent  evaporation  from  and  at  212°,  is  to 
afford  an  intelligible  basis  of  comparison  between  differ- 
ent kinds  of  fuel. 

To  make  such  a  comparison  it  is  necessary  to  know 
the  pressure  and  temperature  of  the  steam ;  the  temper- 
ature of  the  feed  water;  the  number  of  pounds  of  coal 
burned  on  the  grate  (deducting  the  ashes,  if  the  net 
combustible  is  desired) ;  and  the  number  of  pounds  of 
water  evaporated  in  a  given  time.  From  these  last  two 
items  the  ratio  of  coal,  or  net  combustible,  to  evapora- 
tion can  easily  be  determined  by  dividing  the  pounds  of 
water  evaporated,  by  the  pounds  of  coal  burned  in  an 
hour,  a  day,  or  any  other  given  time. 

Example — A  boiler  evaporating  eight  pounds  of 
water  per  pound  of  coal  (net),  the  temperature  of  the 
feed  water  being  85°  Fahr.,  and  the  pressure  of  steam  in 
the  boiler  seventy-live  pounds  per  square  inch,  above  the 
atmosphere ;  what  is  the  equivalent  evaporation  per 
pound  of  coal  (net)  at  atmospheric  pressure  from  and 
at  212°? 

The  total  heat  required  to  generate  one  pound  of 
steam  from  water  at  32°  Fahr.,  under  a  constant  pressure 


EVAPORATIVE    POWER    OF    COAL.  19* 

of  seventy-five  pounds  per  square  inch  is  1176  units  of 
heat.  The  water  entering  the  boiler  at  a  temperature-' 
of  85°  instead  of  32°,  there  is  a  gain  of  85  —  32  =  53 
degrees.     Then. 

1170  —  53  =  1123  units  of  heat. 

The  units  of  heat  required!  to  convert  one  pound  of 
water  at  212°  into  steam,  at  atmospheric  pressure,  is, 
966.     Then, 

1 123  -:-  '."V,      1 .16,  the  multiplier. 

1.16 

8  pounds  jof  coal. 

9.28  = 

the  equivalent  evaporation  per  pound  of  coal  (net),  at 
atmospheric  pressure,  from  and  at  a  temperature  of  212G. 

Second  Method — \\  nen  the  total  heat  of  combustion 
of  one  pound  of  combustible  is  known. 

In  this  case,  the  equivalent  evaporative  power  of  the 
combustible  at  atmospheric  pressure,  from  and  at  a  tem- 
perature of  212°,  maybe  determined  by  dividing  the 
number  of  heat  units  of  the  combustible  by  ^*j6,  the 
number  of  heat  units  required  to  convert  water  at 
212°  into  steam   ;ti   atmospheric  pressure. 

EXAMPLE  1 — What  number  of  pounds  of  water. 
at  212°,  will  one  pound  of  bituminous  coal,  having 
13,624  heat  units  as  its  total  heat  of  combustion,  convert 
into  steam  at  atmospheric  pressure? 

13,624       ,  ,  ,  ,       , 

I  \.  1  pounds  «>t  water. 
(14) 


194  COMBUSTION   OF   COAL. 

Example  2 — The  same  as  the  preceding  except  the 
feed  water  to  be  at  64°  instead  of  212°?     Then, 

212°  —  64°  =  148°  difference. 

966°  +  148°  =  1114°  the  new  divisor. 

13,624 


1114 


;  12.23  pounds  of  water. 


And  in  this  manner  for  any  temperature  between  82c 
and  212°. 


CHAPTER  X. 

HEAT. 

'Theory  of  Heat — Mechanical  Force — Chemical  Action — Relation  of 
Atomic  Weights  to  Specific  Heat — Specific  Heat  of  Simple 
Gases — Specific  Heat  and  Atomic  Weight  of  Elementary  Sub- 
stances— Specific  II  eat — Specific  Heat  of  Water  in  its  Three 
States — Specific  Heat  of  Fuels — Specific  Heat  of  Gases — Latent 
Heat — Latent  Heat  of  Fusion — Latent  Heat  of  Evaporation — 
Mechanical  Theory  of  Heat — Joule's  Equivalent — Apparatus 
Employed  by  Joule — Unit  of  Heat. 

The  theory  of  heat  now  accepted  is  known  as  the 
dynamical,  or  the  mechanical  theory,  and  is  so  called 
because  it  is  believed  that  heat  and  mechanical  force  are 
identical,  and  convertible  one  into  the  other. 

The  relation  between  heat  and  mechanical  force  is 
now  expressed  by  a  numerical  equivalent,  which  is  so 
nearly  true  that  it  serves  to  show  not  only  the  probable 
permanence  of  this  theory,  but  indicates,  also,  that  these 
relations  arc  determined  by  a  fixed  numerical  law. 

From  the  vast  number  of  experiments  in  the  genera- 
tion of  heat  by  mechanical  processes;  by  friction;  by  the 
in  rest  of  motion,  either  gradually  or  by  percussion;  by 
the  change  in  quantity  of  heat  observed  in  the  case  of 
expansion,  etc.,  lias  led  investigators  to  the  conclusion 
thai  lnai  i>  simply  a  motion  of  ultimate  particles,  and 
that  the  molecular  structure  of  bodies  has  much  to  do 
with  their  capacities  for  heat;  and,  an  increase  or 
decrease  of  temperature  is  simply  ;m  increase  or  decrease 
of  molecular  motion. 


196  COMBUSTION    OF    COAL. 

As  all  chemical  changes  are  either  atomic  or  molec- 
ular, and  as  all  differences  in  the  temperature  of  bodies 
are  due  to  the  changes  in  their  molecular  condition,  it 
would  appear  that  chemical  action,  and  heat,  and 
mechanical  force,  should  he  mutually  convertible.  This 
is  now  a  widely  recognized  truth. 

Chemical  changes  are  always  attended  by  a  change 
in  the  thermal  conditions  of  the  bodies  acted  upon,  in 
which  combinations  as  a  rule,  produce  heat,  while 
decompositions  produce  cold,  or  a  disappearance  of  heat. 
The  amount  of  heat  any  particular  body  is  capable  of 
giving  off  must  be  determined,  as  yet,  experimentally. 
The  researches  of  Favre  and  Silberman,  Andrews, 
Thompson,  Joule,  and  others,  have  given  us  a  very  close 
approximation  to  the  dynamic  value  of  heat,  and  the 
heating  power  of  different  fuels.  The  results  of  their 
investigations,  so  far  as.it  affects  the  combustion  of  coal, 
are  given  elsewhere  in  this  volume. 

Relation  of  Atomic  Weights  to  Specific  Heat — In  regard 
to  the  atomic  weights  and  their  relation  to  specific  heat, 
it  is  a  noteworthy  fact,  that  as  the  specific  heat  increases 
the  atomic  weight  diminishes,  and  vice  versa;  so  that  the 
product  of  the  atomic  weight  and  specific  heat  is,  in 
almost  all  cases,  a  sensible  constant  quantity  (30).  The 
most  important  experiments  on  the  specific  heat  of  elas- 
tic fluids  we  owe  to  M.  Regnault.  He  determined  the 
quantities  of  heat  necessary  to  raise  equal  volumes  of 
them,  through  the  same  number  of  degrees.  Calling 
the  specific  heat  of  water  1,  here  are  some  of  the 
results  of  this  invaluable  investigation : 


RELATION  OF  ATOMIC  WEIGHTS  TO  SPECIFIC  HEATf 


197 


Table  XXIII. 
Specific  Seat  of  Simple  Gases. 


SPECIFIC  HEATS. 

EQUAL 
WEIGHTS. 

EQUAL 
VOLUMES. 

Air 

0.237 
0.218 
0.244 
3.409 
0.121 
0.055 

(1.240 

Nitrogen 

0.237 

Hydrogen 

0.236 

Chlorine '. 

0.296 

Ill'  iinine 

0.304 

We  have  already  arrived  at  the  conclusion  that,  for 
equal  weights,  hydrogen  would  be  found  to  possess  six- 
teen times  the  amount  of  heat  possessed  by  oxygen,  and 
fourteen  times  that  of  nitrogen,  because  the  hydrogen 
contains  sixteen  times  the  number  of  atoms,  in  one  case, 
and  fourteen  times  the  number  in  the  other.  We  here 
find  this  conclusion  verified  experimentally.  Equal 
volumes,  moreover,  of  all  these  gases  contain  the  same 
number  of  atoms,  and  hence  we  should  infer  that  the 
specific  heats  of  equal  volumes  ought  to  be  equal.  They 
arc  nearly  so  for  oxygen,  nitrogen  and  hydrogen;  but 
chlorine  and  bromine  differ  considerably  from  the  other 
elementary  ga>e<. 

Table  XX I V  on  the  next  page  shows  the  specific 
heal  of  the  elementary  substances  in  table  H,  together 
with  their  atomic  weights  and  products,  the  gases  in 
table  Will  excepted: 


198 


COMBUSTION    OF    COAL. 


Table  XXIV. 

NAME. 

SYMBOL. 

SPECIFIC 
HEAT. 

ATOMIC 
WEIGHT. 

PRODUCTS. 

Aluminum 

Al 
Ca 

C 

Fe 

Mg 

P 

K 

Si 

S 

0.2143 

0.1670 
0.2415 
0.1138 
0,2499 
0.1887 
0.1696 
0.1774 
0.1776 

27.5 
40 

12. 

56> 
24 
31 

39 

28 
32 

5.89 

( !arbon  (charcoal) 

6.68 
2.90 

Iron 

6.37 

Magnesium 

6.00 

Phosjihorus 

5.85 

0.61 

.Silicon  (cry&talized) 

4.97 

Sulphur 

5  68 

It  will  be  observed,  In  examining  the  column  of  pro- 
duets  formed  by  multiplying'  the  specific  heat  and  the 
atomic  weights  together,  that  there  is  a  very  close 
approximation  to  a  constant  product.  Neglecting  car- 
bon and-  silicon,  which  are,  apparently,  exceptions — 
and  this  may  in  part  be  accounted  for,  as  they  are  so 
diverse  in  their  known  or  ordinary  physical  conditions, 
they  have  not,  in  general,  the  uniform  type  of  conditions 
which  are  so  characteristic  of  most  of  the  other  ele- 
ments— aside  from  these,  we  rind  the  lowest  in  this  table 
to  be  5.68,  and  the  highest  6.61,  making  an  average  of 
0.07. 

If  we  were  to  obtain  an  average  of  all  the  products 
so  far  as  known,  it  will  be  found  to  closely  approximate 
6.34.  This  is  too  close  to  be  accidental,  and  the  usual 
explanation  is  (3),  that  the  atoms  of  the  different  ele- 


SPECIFIC    HEAT.  199 


ments  have  the  same  capacity  for  heat,  and  hence,  that 
masses  of  the  elementary  substances  containing  the  same 
number  of  atoms,  must  have  the  same  capacity  for  heat 
when  under  similar  physical  conditions;  the  constant 
product  being*  the  amount  of  heat  required  to  raise  the 
temperature  of  such  masses  to  the  same  degree. 

Specific  Heat — The  specific  heat  of  a  substance 
means  the  quantity  of  heat,  expressed  in  thermal  units, 
which  must  be  transferred  to  or  from  a  unit  of  weight 
(such  as  a  pound)  of  a  given  substance,  in  order  to  raise 
or  lower  its  temperature,  by  one  degree,  at  a  certain 
specific  temperature. 

According  to  the  definition  of  a  thermal  unit,  the 
specific  heat  of  liquid  water,  at  and  near  its  temperature 
of  maximum  density,  is  "///'/y;  and  the  specific  heat  of 
any  other  substance,  or  of  water  at  any  other  part  of 
the  scale  of  temperatures,  is  the  ratio  of  the  iceight  of 
■  at  or  near  39.1°  Fahr.,  which  has  its  temperature 
altered  one  degree  %  the  transfer  of  a  given  quantity  of  heat, 
to  the  weight  of  th  other  subslana  under  consideration,  which 
has  its  temperature  altered  one  degree  by  the  transfer  of  an 
,  qual  quantity  of  '■>  at  (22). 

The  specific  heat  of  a  substance  is  sometimes  called 
its  ••  caj  acity  for  heat." 

The  Bpecific  beats  of  water  in  the  solid,  liquid  and 
gaseous  state,  are  as  follows: 

[ce 0.504 

Water 1.000 

m 0.622 


200  COMBUSTION   OF    COAL. 

showing  that,  in  the  solid  state,  as  ice,  the  specific  heat 
of  water  is  only  half  that  of  liquid  water;  and  that,  in 
the  gaseous  state,  it  is  little  more  than  that  of  ice,  or 
nearly  five-eighths  that  of  liquid  water. 

Table  XXV. 
Specific  Heat  of  Fuels.     (Afteb  Regjjault.) 


WATER  AT 

32°=1. 


Oak  wood I  .570 

Wood  charcoal  .2415 

Coal  and  coke,  average  (Rankine) .200 

Coke  of  cannel  coal '  .20307 

Anthracite  coal,  Welsh .20172 

Anthracite  coal,  American  '     .201 

I 

For  all  ordinary  calculations  it  is  a  near  enough 
approximation  to  assume  that 

Woods  average  one-half  the  specific  heat  of  water. 
Coal  and  coke,  two-tenths  the  specific  heat  of  water. 
Wood  charcoal,  one-fourth  the  specific  heat  of  water. 

Note — Slight  fractional  differences  will  doubtless  !"■  observed  in  the  specific 
beats  of  the  same  substances.  These  have  been  calculated  by  different  observers 
widely  separated,  and  are  really  marvels  of  accuracy,  notwithstanding  the  dillerences, 
which  are  so  slight  as  to  cause  no  material  error  in  any  calculation.  B. 


LATENT    HEAT. 


201 


Table  XXVI. 
Showing  the  Specific  Heat  of  Gases  —  Water  at  32°  Fahr  =  1. 


Carbonic  acid 

Oxygen 

Air 

Nitrogen 

Carbonic  oxide 

defiant  gas 

] [ydrogen 

Vapor  of  alcohol 

Gaseous  steam 

Light  carbureted  hydrogen 


BPECIFIC   HEAT  FOR 
EQUAL   WEIGHTS. 


AT 
CONSTANT 
PRESSURE. 


WATER=1 

0.2164 

0.2182 
0.2377 
(1.2440 
(1.247V 
0.3694 
3.4046 
0.4513 
0.4750 
0.5929 


AT 
CONSTANT 
VOLUME. 

(REAL 
SPECIFIC 
HEAT.) 


WATER=1 

0.1714 
0.1559 
0.1688 
0.1740 
.  0.1 70S 
0.2992 
2.4096 
0.4124 
0.3643 


SPECIFIC  HEAT  FOR 
EQUAL    VOLUMES. 


AT 
CONSTANT 

PRESSURE. 


AIR=.2377 
AS  IN  COL.  2 

0.3308 
0.2412 
0.2377 
0.2370 
0.2399 
0.3572 
0.2356 
0.7171 
0.2950 
0.3277 


AT 
CONSTANT 

VOLUME. 


AIR=.1<  188 
AS  IN  COL.  3 

0.2620 
0.1723 
0.1688 
0.1690 
0.1711 
0.2893 
0.1667 
0.05.".:; 
0.2262 
0.2588 


Latent  Heat — Is  that  quantity  of  heat  which  disap- 
pears, or  becomes  concealed  in  a  body  while  producing 
some  change  in  it  other  than  a  rise  in  temperature.  By 
exactly  reversing  that  change,  the  quantity  of  heat 
which  had  disappeared  is  re-produced. 

If  heat  is  applied  to  a  block  of  ice,  having  a  temper- 
ature, say,  ten  or  fifteen  degrees  below  the  freezing  point 
of  water,  the  temperature  will  continue  to  rise  with  each 
increment  of  heat  until  32  Fahr.  is  reached,  when  the 
melting  of  the  ice  will  begin;  it  will  be  observed   thai 


202  COMBUSTION    OF    COAL. 

the  heat  being  transmitted  to  the  ice,  as  before,  there  is 
no  corresponding  rise  in  temperature,  either  in  the  ice 
or  the  water  in  contact  with  it,  so  long  as  any  ice 
remains  unmelted  ;  and,  that  during  the  process  of  melt- 
ing the  temperature  of  the  water  is  constant,  and  at  32° 
Fahr. 

Latent  Heat  of  Fusion — This  change  of  state  from 
solid  to  liquid,  in  the  melting  of  ice,  requires  one  hun- 
dred and  forty-three  units  of  heat,  the  temperature 
being  32°  as  at  first ;  the  heat  in  this  case  does  not  raise 
the  temperature  of  the  ice,  but  disappears  in  causing  its 
condition  to  change  from  the  solid  to  the  liquid  state. 
According  to  our  present  theory  (30),  the  heat  expended 
in  melting  is  consumed  in  conferring  potential  energy 
upon  the  atoms.  It  is,  virtually,  the  lifting  of  a  weight. 
The  act  of  liquefaction  consists  of  interior  work — of 
work  expended  in  moving  the  atoms  into  new  positions. 
This  is  called  the  latent  heat  of  fusion. 

Latent  Heat  of  Evaporation — After  the  ice,  in  the 
above  experiment,  has  entirely  disappeared,  the  applica- 
tion of  heat  being  continued,  the  thermometer  will  begin, 
and  will  continue  to  rise  until  212°  Fahr.  is  reached, 
when  it  again  becomes  stationary,  and  will  remain  so 
as  long  as  evaporation  is  continued  at  atmospheric 
pressure. 

Again,  it  will  be  observed  that  heat  disappears  in 
the  change  of  the  water  from  the  liquid  to  the  gaseous 
state.  Experimentally  this  has  been. ascertained  to  be 
nine  hundred  and  sixty-six  units  of  heat.     From  the 


MECHANICAL    THEORY    OF    HEAT.  203 

freezing  to  the  boiling  point  there  are  212 — 32  =  180°; 
so  we  find  that  966-^180  =  5.37  times  as  much  heat 
is  required  to  convert  water  into  steam,  at  atmos- 
pheric pressure,  as  it  requires  to  raise  the  temper- 
ature from  the  freezing  to  the  boiling  point.  In  the 
preceding  section,  the  theory  was  given  that  the  heat 
expended  in  melting  the  ice  was  consumed  in  conferring 
potential  energy  upon  the  atoms.  In  regard  to  the 
steam,  or  the  evaporation  of  the  water,  the  heat  is  con- 
sumed in  pulling  the  liquid  molecules  asunder,  confer- 
ring upon  them  still  greater  potential  energy. 

When  the  heat  is  withdrawn,  the  vapor  condenses, 
the  molecules  clash  with  a  dynamic  energy,  equal  to 
that  which  was  employed  to  separate  them,  and  the 
precise  quantity  of  heat  then  consumed  re-appears  (30). 
The  act  of  vaporization  is,  for  the  most  part,  interior 
work;  to  which,  however,  must  be  added  the  exterior 
work  of  forcing  back  the  atmosphere,  when  the  liquid 
becomes  vapor. 

Mechanical  Theory  of  Heat — Professor  Rankine's 
statement  of  the  first  law  of  thermodynamics  is  that, 

"Ilatt  ami  mrrhanU-al  cncnjii  are  mutually  convertible; 
and  heat  requires  for  its  'production,  and  produces  by  its  dis- 
appt  arana  ,  mechanical  energy  in  the  proportion  of  772  foot- 
pounds  for  each  British  unit  of  heat:  the  said  unit  being 
the  amount  of  heat  required  to  raise  the  temperature  of 
one  pound  of  liquid  water  by  one  degree  Fahrenheit, 
near  the  temperature  of  the  maximum  density  of 
water"  (22). 


204  COMBUSTION    OF    COAL. 

This  is  also  known  as  the  dynamical  theory  of 
heat.  The  772  foot-pounds  as  the  mechanical  equiva- 
lent of  a  heat  unit,  is  often  referred  to  as  Joule's  equiv- 
alent, and  is  so  called  in  honor  of  Dr.  Joule,  of  Man- 
chester, England,  who  was  the  first  to  demonstrate 
experimentally  the  exact  mechanical  equivalent  of  heat. 
This  honor  Dr.  Joule  shares  with  Dr.  Mayer,  a  physi- 
cian in  Heilbronn,  Germany.  The  relations  of  these 
two  men  to  the  mechanical  theory  of  heat  is  thus 
expressed  by  Professor  Tyndall : 

"  The  immortal  investigations,  here  briefly  referred 
to,  place  Dr.  Joule  in  the  foremost  rank  of  physical 
philosophers.  Mayer's  labors  have,  in  some  measure, 
the  stamp  of  a  profound  intuition,  which  rose,  however, 
to  the  energy  of  undoubting  conviction  in  the  author's 
mind.  Joule's  labors,  on  the  contrary,  are  an  experi- 
mental demonstration.  Mayer  thought  his  theory  out, 
and  rose  to  its  grandest  applications ;  Joule  worked  his 
theory  out,  and  gave  it  forever  the  solidity  of  demon- 
strated truth.  True  to  the  speculative  instinct  of  his 
country,  Mayer  drew  large  and  weighty  conclusions 
from  slender  premises;  while  the  Englishman  aimed, 
above  all  things,  at  the  firm  establishment  of  facts.  The 
future  historian  of  science  will  not,  I  think,  place  these 
men  in  antagonism.  To  each  belongs  a  reputation 
which  will  not  quickly  fade,  for  the  share  he  has 
ad,  not  only  in  establishing  the  dynamical  theory  of 
heat,  but  also  in  leading  the  way  toward  a  right 
appreciation  of  the  general  energies  of  the  universe." 


MECHANICAL  THEORY  OF  HEAT. 


205 


The  apparatus  employed  by  Dr.  Joule,  in  the  deter- 
mination of  this  important  constant,  is  represented  in 
figure  7.  A  known  weight  was  connected  by  means 
of  cords  to  a  shaft  /,  mounted  on  "  friction-wheels," 
not  shown  in  the  cut ;  on  this  shaft  a  pully  was  secured, 
and  through  the  medium  of  another  cord  imparted 
motion  to  the  shaft  r,  and  caused  it  to  revolve ;  at  the 
lower  end  of  this  shaft  /•,  were  fitted  eight  sets  of  pad- 
dles,  which,  when    connected   by  means   of  a   pin   P, 


Figure 


revolved  with  it.  To  the  interior  of  the  copper  vessel 
/>'  were  attached  four  stationary  vanes,  cut  out  in  such 
manner  as  to  permit  the  free  revolution  of  the  revolving 
paddles.  Precautions  were  taken  to  prevent  a  transfer 
<>f  heat  from  the  vessel  B,  which  need  not  be  described 
here.  This  vessel  was  filled  with  a  known  weight  of 
water,  ;it  the  temperature  of  its  greatest  density  (30° 
Fahr.j.  and  a  thermometer  /.  was  inserted  in  the  vessel 
/»'.   to   mark   the    rise  in   the   temperature  of  the   water. 


206  COMBUSTION   OF    COAL. 

The  experiment  consisted  in  allowing  the  weight  to 
descend  by  its  own  gravity,  and  through  the  medium  of 
the  cords  to  cause  the  paddles  to  revolve  and  agitate  the 
water  in  the  vessel  B. 

Acting  on  the  assumption  that  wherever  there  is 
motion  there  must  be  an  evolution  of  heat,  it  was 
expected  that,  a  weight  falling  through  a  certain  dis- 
tance must  occasion  a  certain  rise  in  temperature  in  a 
certain  weight  of  water,  this  was  found  to  he  true;  and 
after  many  hundreds  of  experiments,  extending  through 
several  years,  it  was  finally  fixed  by  Dr.  Joule  at  772 
pounds  raised  one  foot  high  against  the  action  of  grav- 
ity, as  the  mechanical  equivalent  of  the  quantity  of  heat 
necessary  to  raise  the  temperature  of  one  pound  of 
water  through  one  degree  at  its  temperature  of  maxi- 
mum density,  or,  from  39  to  40  Fahrenheit. 

The  following  are  the  values  of  Joule's  equivalent 
for  different  thermometric  scales,  and  in  French  and 
British  units: 

One  British  thermal  unit,  or  one  degree  Fahrenheit  in  one 
pound  of  water  =  772  foot-pounds. 

One  French  thermal  unit,  or  one  degree  Centigrade  in  one 
kilogramme  of  water  =  423.55  (say  424)  kilogrammetres. 

One  degree  Centigrade  in  one  pound  of  water  =  1389.6,  or  very 
nearly  1390  foot-pounds. 

One  calorie,  or  French  thermal  unit  =  3.9G8  British  heat  units. 

One  British  heat  unit=  .252  calorie. 

Unit  of  Heat — This  is  a  conventional  term  express- 
ing the  quantity  of  heat  required  to  raise  the  tempera- 
ture of  one  gram  of  water  from  4°  to  5°  Centigrade. 


UNIT   OF    HEAT.  207 


This  is  the  French  unit,  and  that  principally  used 
by  chemists  and  scientific  writers;  it  is  sometimes 
spoken  of  as  a  calorie. 

The  unit  in  more  general  use  among  English  and 
American  engineers  is  the  quantity  of  heat  required  to 
raise  the  temperature  of  one  pound  of  water  from  39° 
to  40°  Fahr.  This  is  the  unit  selected  for  use  in  this 
book. 

A  thermal  unit  and  a  unit  of  heat  mean  the  same 
thing.  The  use  of  the  word  calorie  should  never  be 
considered  a  synonym  for,  and  should  not  be  used  to 
express  an  English  unit,  but  should  be  referred  to  only 
as  the  French  unit. 

Many  writers,  inadvertantly  perhaps,  give  the  unit 
of  heat  as  that  necessary  to  raise  one  gram  of  water 
from  0°  to  1°  Cent.,  or  one  pound  from  82°  to  33°  Fahr. 
Tins  is  an  error;  it  is  the  raising  of  the  temperature  of 
water  through  one  degree  at  its  temperature  of  greatest 
density:  this  on  the  Centigrade  thermometer  is  3°.94, 
or  39.1°  Fahr. 

It  will  be  near  enough,  however,  for  all  practical 
purposes,  to  call  the  temperature  of  greatest  density  of 
water  4°  Cent.,  or  39°  Fahr. 


CHAPTER  XL 

THE  CONSTRUCTION  OF  FURNACES. 

Construction  Depends  on  the  Fuel — Conditions  Attached  to  a  Good 
Furnace — Why  Ordinary  Furnaces  are  so  Wasteful — Volatiliza- 
tion of  Gases  in  the  Furnace  —  Quantity  of  Air  Required  — 
Force  Blast — Description  of  a  Reverberatory  Furnace  —  Its 
Advantages — Increase  of  Efficiency  by  the  Use  of  Hot  Air — 
Loss  by  Chimney  Draft. 

This  chapter  is  made  up  of  selections  from  a  paper 
read  before  the  "  Edinburgh  and  Lieth's  Engineers' 
Society,"  by  Mr.  Charles  Fairbairn,  a  prominent  manu- 
facturer of  iron,  who  has  given  this  subject  a  great  deal 
of  personal  attention. 

His  views  are  based  upon  correct  theory,  and  con- 
firmed by  actual  trial. 

It  is  probable  that  much  the  same  method  of  econo- 
mizing fuel,  as  that  suggested  by  Mr.  Fairbairn,  will 
sooner  or  later  be  largely  employed  in  steam  boiler 
furnaces;  by  this,  is  meant,  the  generating  of  an  intense 
heat,  and  in  large  quantities,  in  a  separate  chamber, 
instead  of  directly  under  the  boiler.  The  coal  will 
probably  be  fed  from  underneath  the  fire;  that  is,  the 
blast  will  pass  through  the  fresh  charge  of  coal  in  some 
manner  analogous  to  that  shown  in  the  engraving  of  Mr. 
Fairbairn's  furnace;  with  any  such  arrangement  as  this,  a 
force  draft  becomes  a  necessity;  and  by  the  use  of  a 
heated   blast,   instead    of  a   cold    one,   a   much   higher 


CONSTRUCTION    OF    FURNACE?.  209 

degree  of  economy  may  be  readied  than  is  possible  by 
ordinary  firing,  and  natural  draft. 

"  The  great  variety  of  kinds  of  fuel,  although  they 
contain  nearly  the  same  ingredients,  but  in  different. 
proportions,  renders  it  a  somewhat  difficult  task  to 
define  what  a  .furnace  should  be.  Hydrocarbons,  such 
as  pitch,  tar,  naptha  and  petroleum,  have  all  to  pass 
into  the  gaseous  state  before  they  can  be  burned. 

"Coke,  which  is  coal,  with  all  the  bituminous  and 
gaseous  portions  taken  out  of  it,  is  nearly  pure  carbon, 
with  a  small  proportion  of  ash. 

"Anthracite  coal,  which  is  very  similar  in  its  nature 
to  coke,  is  wholly  composed  of  free  carbon.  It  is  liable; 
to  split  and  tall  into  powder;*  it  burns  without  flame, 
and  very  little  smoke,  and  requires  a  very  strong 
draught. 

••  Bituminous  coal,  again,  of  which  there  is  an 
immense  variety,  has  a  smaller  proportion  of  carbon. 
with  a  mixture  of  hydrogen  and  oxygen.  From  this  it 
will  appear  evident  that  special  provision  must  be  made 
for  a  Bupply  of  air  to  support  combustion  instead  of  the 
different  kind-  of  fuel  used.  Thus,  a  furnace  arranged 
for  burning  bituminous  coal  might  be  very  wasteful  in 
burning  anthracite  coal ;  due  regard  then  must  be  paid 
in  all  cases  to  the  character  of  the  fuel  employed. 

The  indispensable  conditions  attached  to  a  good 
furnace,  for  all  kinds  of  fuel,  arc, 

1.     A  goo,|  draft,  which  can  be   regulated   at  will,  so 

as  to  avoid  forcing  the  fire  too  much. 

'I"li  i -  r.  hi  ii !,  does  not  apply  to  \ rican  anthracites.      B. 

(15) 


210  COMBUSTION   OF    COAL. 

2.  A  large  and  roomy  combustion  chamber,  sur- 
rounded by  fire  bricks,  and  removed,  if  possible,  from 
the  place  where  the  heat  is  to  be  used. 

3.  That  the  sides,  or  walls  of  a  furnace,  have  at  least 
ten  thicknesses  of  bricks  nearest  the  fire,  and  an  outer 
wall  having  an  air  space  between  of  about  three  inches. 

4.  That  the  supply  of  air  to  the  furnace  can  be 
regulated  at  will. 

"I  do  not  think  we  can  always  command  these  con- 
ditions, especially  in  a  furnace  constructed  on  the  prin- 
ciple of  depending  on  atmospheric  pressure  for  draught; 
and  the  reason  is  obvious,  becau§e  in  order  to  obtain  a 
good  and  equal  draught  we  require  not  only  a  tall 
chimney,  but  the  chimney  must  be  maintained  at  a  high 
temperature,  about  six  hundred  degrees;  and  as  the 
temperature  within  the  furnace  may  be  assumed  at 
twenty-five  hundred  degrees,  the  abstraction  of  this 
large  quantity  of  heat  to  keep  the  chimney  at  a  suffici- 
ently high  temperature,  amounts  to  one-fourth  of  the 
heat,  and  consequently  of  the.  fuel  which  is  expended  for 
that  purpose  alone.  Nor  is  this  the  only  drawback. 
The  attendant  on  the  furnace,  who  may,  and  often  has 
other  duties  to  perforin,  puts  on  a  heavy  load  of  coal. 
The  flues  and  chimney  are  rapidly  cooled,  and  the  power 
of  the  draught  reduced  at  the  very  time  when  it  should 
be  greatest. 

"  The  second  and  third  conditions  mentioned  may 
assist  in  getting  over  irregularity  in  the  power  of  the 
draught  to  a  certain  extent — that  is,  a  large  and  roomy 


CONSTRUCTION    OF    FURNACES.  211 

combustion  chamber,  and  the  sides  constructed  to  pre- 
vent loss  of  heat. 

"I  do  not  suppose  any  person  who  has  not  had  an 
opportunity  of  seeing  a  furnace  in  operation,  with  the 
heat  confined  in  the  manner  described,  could  have 
believed  the  effect  would  be  so  powerful;  the  inner 
lining  actually  acquires  a  white  heat,  thus  serving  as  an 
accumulator,  which  is  given  out  again  when  the  temper- 
ature of  the  fire  is  reduced  (as  in  the  case  of  a  fresh 
el i urge  of  fuel),  and  at  the  same  time  assisting  to  bring 
the  fresh  fuel  into  active  combustion  more  rapidly;  the 
heat  is  again  returned  to  the  fire  bricks,  and  kept  ready 
for  future  use.  Dr.  Siemens  has  taken  advantage  of 
this  idea,  although  in  quite  a  different  way,  in  his  eele- 
brated  gas  furnace. 

"We  will  now  consider  our  furnaces  as  at  present 
constructed,  and  why  they  are  so  wasteful.  We  hear  a 
great  deal  about  thin  fires  and  regular  charges  in  the 
ordinary;  and  this  is  quite  correct,  inasmuch  as  it  is  the 
only  way  by  which  a  right  supply  of  air  can  be  intro- 
duced to  mix  with  and  consume  the  gases.  There  are 
always  two  dangers  we  have  to  avoid:  One  is  too 
much  air,  which  is  the  least  of  the  evils,  and  in  which 
case  a  very  large  body  of  air  passes  away  unconsumed, 
but  it  also  carries  away  with  it  a  certain  amount  of  heat 
which  cools  the  furnace  and  impedes  the  draught.  The 
Other  evil  of  too  little  air  is  still  more  injurious,  for  the 
gases  having  only  a  small  share  of  the  oxygen  required  are 
burned  into  carbonic  oxide,  and  this  \rvy  often  accounts 
for  the  deficient  supply  of  steam  from  a  boiler,  in  con- 


212  COMBUSTION    OF    COAL. 

sideration  of  the  coal  burned.  But  these  fires  are  liable 
to  burn  into  holes  and  admit  streams  of  cold  air;  nor  is 
this  the  only  objection,  for  when  the  fire  is  fed  with  fresh 
coal,  which  must  of  necessity  be  very  often,  the  new 
coal  absorbs  a  large  proportion  of  the  heat  of  a  thin 
tire,  and  immediately  lowers  the  temperature. 

"The  fire  contains  a  certain  number  of  units  of  heat. 
If  twice  the  quantity  of  coal  was  in  active  combustion, 
there  would  be  double  the  number  of  units  of  heat,  and 
it  could  therefore  more  easily  sustain  the  reduction  of 
temperature  following  a  fresh  charge  of  coal.  I  imasr- 
ine  the  distillation  of  gas  from  coal  or  volatilization  is  a 
process  similar  to  steam  carrying  oft'  the  heat  from 
boiling  water.  The  coal  at  first  becomes  an  absorbant 
of  the  heat  and  then  liberates  the  gases,  and  the  vola- 
tilization of  the  bituminous  portion  of  the  coal  acts  in 
a  similar  manner  to  the  production  of  steam,  as  I  have 
said.*  The  process  is  one  of  the  most  energetic  known 
in  cooling,  because  there  is  so  large  a  portion  of  the 
heat  converted  from  the  sensible  to  the  latent  state. 

"Regarding  the  quantity  of  air  required  in  an  ordi- 
nary furnace  for  the  combustion  of  coal,  I  suppose  very 
few  people  have  any  idea  of  the  magnitude  of  the 
demand. 

"It  is  generally  given  as  300  cubic  feet,  or  24  pounds 
of  air  to  one  pound  of  coal.  Let  us  place  this  in 
another  light: 

"In  my  own  establishment  at  Gateshead  I  have  seven 
furnaces,  each  of  which  uses  about  one  ton  of  fuel  per 
day.  in  all  about  seven  tons;  therefore  7X24  =  108  tons 


CONSTRUCTION    OF    FURNACES. 


213 


of  air  required.  Again,  a  pound  of  coal  requires  about 
300  cubic  feet  of  air.  If  we  imagine  the  108  tons  of 
air  made  into  a  long  stream  of  one  square  foot  in  area, 
the  total  length  will  be  21,381  miles  in  length.  Another 
great  cause  of  the  loss  of  heat,  as  before  stated,  is  the 
quantity  of  heat  continually  passing  away  to  the  chim- 
ney. 


''One  difficulty — that  is,  regulating  the  supply  of  air 
to  the  furnace — can  only  be  overcome  by  artificial 
means,  either  by  a  fan-blast  or  steam-jet.  I  believe  the 
time  is  fast  approaching  when  the  supply  of  air  to 
furnaces  will  be  regulated  in  this  way.  as  the  most 
efficient  and  economical,  and  as  obviating  a  great  many 
of  the  faults  of  our  present  furnace. 

"  The  idea  is  old  enough.  However,  the  arrangement 
of  the  furnace,  I  will  describe  presently,  may  or  may 
not  be  new.  1  never  saw  it  before,  nor  am  I  aware  that 
anything  of  the  same  kind  has  been  tried,  and  to  it  I 

have  addeil  a  supply  of  air   by    mean-    of  a    blower.      In 

this  furnace,  of  which    the  drawing  is  a  longitudinal 


214  COMBUSTION    OF    COAL. 

section,  the  coal  is  introduced  from  the  top,  and  is 
always  on  top  of  the  incandescent  fuel,  at  the  side  of 
the  furnace  furthest  from  the  place  where  the  flame 
makes  its  escape. 

"The  hearth  is  of  fire-brick,  and  during  the  meal 
hours  all  the  ashes  and  clinkers  are  removed  by  the 
hole  in  the  side  of  the  furnace. 

"  The  blast  is  introduced  above  the  new  coals,  and 
passes  through  them.  As  the  coals  begin  to  ignite,  all 
the  inflammable  gases  are  forced  through  the  fire,  and  at 
the  same  time  mixed  with  air. 

"The  advantages  with  this  kind  of  furnaces  seem  to 
be  the  following;:. 

1.  The  whole  of  the  gaseous  products  are  made 
available. 

2.  There  is  entire  absence  of  smoke,  in  consequence 
of  perfect  combustion. 

3.  There  is  a  smaller  quantity  of  air  required,  prob- 
ably about  one-fourth  less;  that  is,  about  eighteen 
pounds  of  air  to  one  pound  of  coal. 

4.  No  increase  of  temperature  above  the  external 
air  is  required  in  the  chimney,  and  the  escaping  heat 
from  the  furnace  can  be  used  for  other  purposes. 

5.  A  higher  temperature  in  the  furnace,  and  more 
rapid  circulation  of  heat. 

6.  The  perfect  control  which  the  attendant  has 
over  the  furnace  as  regards  temperature,  getting  the 
fire  lighted  and  into  operation  in  less  time,  when  they 
have  not  been  in  use. 


CONSTRUCTION    OF   FURNACES.  215 

"There  is  also  another  very  important  point  in  con- 
nection with  this  method  of  making  re-heating  fur- 
naces— that  the  air  can  be  so  nicely  adjusted  by  means 
of  the  blast  and  damper,  as  to  insure  that  nearly  all  the 
oxygen  will  be  taken  up  by  the  carbon  and  gases,  in 
consequence  of  which  the  iron  is  heated  with  scarcely 
any  loss  from  oxide  or  scale.*  The  balance  of  pressure 
can  be  made  so  that  even  where  there  are  unprotected 
inlets  to  the  interior  of  the  furnace,  the  flame  can  be 
made  to  come  to  the  edge  of  the  open  space.  I  believe 
the  efficiency  of  the  furnace  might  be  largely  increased 
by  using  hot  air,  which  might  be  done  by  passing  it 
through  pipes  or  brick  work  placed  in  the  flues;  for  if 
we  have  the  heat  of  the  furnace  twenty-live  hundred 
decrees,  and  the  entering  air  heated  to  five  hundred 
degrees,  the  result  would  necessarily  be  a  great  saving. 
<  >u  this  point  we  have  the  experiences  of  blast  furnaces 
as  an  indication  of  what  might  be  saved  by  this  means 
alone. 

1  have  again  to  mention  that  a  furnace,  which  will 
suit  admirably  for  one  kind  of  coal,  will  not  answer  for 
another.  Thus,  the  conditions  under  which  coke  and 
anthracite  coal  enter  into  combination  with  oxygen,  are 
much  Less  complex  than  in  burning  bituminous  coal, 
and  the  great  point  to  be  observed  is.  that  a  large  quan- 
tity be  kept  on  the  bars:  there  is  not  so  much  danger 
of  the  carbon  passing  away  without  its  supply  of 
oxygen — in  fact  it  can  not  do  so.  as  it  can  not  rise   until 

I  'lie  reader  «i!i  c.i"  coarse  understand  thai  the  engraving  is  ;i  section  of,  and  tbe 
beating  of  the  iron  refers  to  a  puddling  furnace.    B. 


216  COMBUSTION    OF    COAL. 

it  has  its  quantity  of  oxygen  to  liberate  it.  In  bitumin- 
ous coal  the  bituminous  portion  is  only  serviceable  for 
heat  when  converted  into  gas,  while  the  carbonaceous 
portions  are  consumed  only  in  the  solid  state,  and  they 
must  be  separated,  as  explained,  before  they  can  be 
consumed.  Thus,  when  coke  or  anthracite  coal  are 
burned,  the  products  are  carbonic  acid  gas,  and  nitro- 
gen; while  with  bituminous  coal  we  have  carbureted 
hydrogen,  nitrogen  and  carbonic  acid  gas,  or  oxide. 

"It  is  supposed  that  in  some  instances  we  have  real- 
ized about  seventy  per  cent,  of  the  theoretical  heat  in 
fuel.  This,  I  would  be  inclined  to  doubt.  We  have 
seen  that  with  the  ordinary  furnace  we  lose  about 
twenty-five  per  cent,  in  getting  a  draught;  we  have  to 
add  to  this  loss  from  small  coal,  too  much  or  too  little 
air;  the  products  of  combustion.  Hying  oft'  to  the  chim- 
ney at  a  speed  of  thirty  feet  in  a  second  in  some 
instances,  it  must  be  abundantly  clear  that  fifty  per 
cent,  of  the  heat  of  fuel  we  use  is  lost.  It  has  been 
stated  that,  in  some  processes  in  connection  with 
the  manufacture  of  iron,  the  quantity  of  fuel  used 
was  sufficient  to  produce  the  desired  result  four- 
teen times  if  properly  applied.  I  think  it  is  clear  we 
begin  by  placing  the  chimney  at  the  wrong  end  of  the 
furnace,  and  the  air  ought  to  be  driven  in,  not  drawn 
through.  We  have  seen  when  a  blast  is  used  we  can 
have  a  pressure  in  the  furnace  sufficient  to  balance  the 
pressure  of  the  atmosphere.  The  waste  heat  could  also 
be  made  to  do  work  in  passing  away.  I  dare  say  most 
of  us  now   present  can  recall  instances   to  our   mind 


CONSTRUCTION    OF    FURNACES.  217 

where  a  number  of  furnaces  are  used,  and  where  the 
heat  of  one,  if  it  could  be  retained  and  applied,  would 
be  amply  sufficient. 

"  The  blast,  then,  is  the  only  means  of  doing  it,  and 
I  do  not  think  the  time  is  far  distant  when  the  hideous 
pillars  we  seem  so  fond  of  now  will  be  no  longer  seen," 


CHAPTER   XII 


MECHANICAL    FIRING. 


Objections  to  Hand  Firing — Continuous  Firing — The  Requirements 
of  a  Self-feeding  Mechanism — Description  of  M.  Holroyd 
Smith's  Furnace-Feeder. 

There  are  several  objections  to  hand-firing,  when 
taken  in  connection  with  steam  boiler  furnaces.  In 
order  to  get  the  best  results  from  such  a  furnace  the 
tiring  should  be  as  nearly  constant  as  possible,  in  order 
that  chemical  action  may  go  on  undisturbed.  Hand 
tiring  must,  from  its  nature,  be  intermittent,  and  there- 
fore irregular.  When  the  fire  is  brisk,  and  a  boiler 
steaming  rapidly,  the  opening  of  the  furnace  doors  in 
order  to  admit  a  fresh  charge  of  fuel,  and  thus  allowing 
a  draft  of  cold  air,  often  below  the  freezing  point  of 
water,  to  impinge  against  the  heated  plates  of  the 
boiler,  at  the  same  time  lowering  the  temperature  of 
the  gases  in  the  furnace,  and  added  to  this,  the  deaden- 
ing of  a  brisk  tire  by  a  fresh  charge  of  coal,  always  in 
excess  of  actual  requirements,  and  too  often  unevenly 
spread,  is  certainly  not  conducive  to  the  highest 
economy. 

The  advantages  of  continuous  firing  were  pointed 
out  early  in  the  present  century,  and  a  great  number  of 
devices  have  been  tried  from  time  to  time,  many  of 
which  have  long  since  disappeared  to  give  place  to  better 
contrivances  to  this  end. 


MECHANICAL    FIRING.  219 


The  ideal  mechanism  for  feeding  steam  boiler  fur- 
naces, must,  in  addition  to  supplying  the  fuel,  distribute 
it  in  such  manner  that  it  may  be  economically  burned; 
it  must  admit  a  proper  supply  of  air  at  the  right  time 
and  place  to  insure  perfect  combustion,  and  prevent 
smoke ;  it  should  be  adapted  to  the  use  of  line  or  slack 
coal,  and  preferably,  granular  fuel;  it  should  be  so 
arranged  as  to  admit  of  a  forced  draft  being  used;  it 
should  admit  the  examination  of  the  fire  at  all  times, 
and  the  stirring  or  slicing  of  it  whenever  needed;  it 
must  permit  the  ready  removal  of  clinker  from  the  grate 
bars  as  fast  as  it  accumulates;  it  must  permit  the  ready 
removal  of  ashes  from  the  fire,  while  in  actual  operation, 
without  breaking  it  up,  or  destroying  its  efficiency;  the 
parts  should  be  few  and  free  from  complications;  all 
moving  mechanism  should  be  protected  from  the  heat 
and  action  of  the  fire;  it  should  consist  of  parts  easily 
made  and  repaired;  and,  as  a  whole,  must  combine 
utility,  simplicity,  economy,  ease  of  management  and 
durability. 

The  furnace-feeder,  described  below,  was  devised  by 
Mr.  M.  Ilolroyd  Smith,  of  England,  and  appears  to 
combine  most  of  the  requirements  enumerated  above; 
and.  in  addition,  it  will  be  observed  that  the  coal  is 
forced  into  the  fire  from  underneath,  so  that  the  volatile 
gases  are  extracted  by  the  incandescent  fuel  above  it, 
and  burnl  as  fast'as  evolved  from  the  fresh  supplies. 
There  arc  many  other  forms  of  furnace-feeders  in  use, 
and  doing  good  service. 


220  COMBUSTION    OF    COAL. 


M.  HOLROYD  SMITH'S  FURNACE  FEEDER/1 

"This  invention  relates  to  improved  apparatus  for 
supplying  the  fuel  by  self-acting  mechanism,  designed 
to  supply  the  fuel  from  underneath  the  fire,  the  object 
being  to  insure  more  complete  combustion,  and,  as  a 
consequence,  increased  economy  of  fuel. 

"This  invention  relates  to  an  improved  apparatus  for 
feeding  fuel  to  the  grate  of  a  furnace;  and  consists  in 
combining  the  grate-bars  of  the  furnace  with  troughs 
or  screw-cases,  that  are  placed  between  and  communi- 
cate with  the  grate-bars,  and  are  connected  at  one  end 
to  a  feed-trough  and  a  hopper,  said  screw-cases  contain- 
ing each  a  screw  or  worm,  all  being  so  arranged  that 
the  fuel  is  fed  by  the  screws  or  worms  from  the  hopper 
and  feed-trough  into  the  screw-cases,  and  from  the 
screw-cases  directly  upon  the  grate-bars,  all  as  is  here- 
inafter more  fully  described.  The  screw  has,  by  prefer- 
ence, two  threads  of  such  pitch  and  construction  as  to 
exert  an  outward  and  a  propelling  force.  The  propell- 
ing force  of  the  screw  at  its  commencement  is  in  excess 
of  its  lifting  force;  but  at  its  smaller  end  the  lifting 
force  is  greatest,  thereby  insuring  a  uniform  feed  the 
whole  length  of  the  bars. 

"I  prefer  to  use  my  improved  feed  mechanism  in 
connection  with  improved  supplementary  or  auxiliary 
back  grids  or  grates  (placed  off  the  ends  of  the  furnace- 
bars)  and  apparatus  for  operating  the  same,  so  as  to 
remove  the  spent  fuel  or  ashes  therefrom. 

^Patented  January  8,  1878. 


M.  HOLROYD  SMITH'S  FURNACE  FEEDER,       221 

"  The  auxiliary  bars  I  mount  on  axles  within  a  frame, 
and  the  bars  are  connected  by  a  link-motion  that,  by 
working  a  "draw"  or  "push"  rod,  the  bars  will  tilt  and 
throw  off  the  ashes  or  spent  fuel  delivered  on  them 
from  the  main  fire-bars. 

"  The  several  parts  will  be  clearly  understood  by 
reference  to  the  drawings,  aided  by  the  description 
annexed. 

"  Figure  1  is  a  longitudinal  elevation,  partly  in  section, 
illustrating  my  invention  applied  to  an  internally-fired 
single-flue  steam-boiler.  Figure  2  is  a  plan  of  the  same'. 
Figure  3  is  an  elevation  in  cross-section,  on  line  a  b  of 
figure  2.  of  some  of  the  parts  of  the  apparatus.  Figure 
4  is  a  front  or  outside  elevation.  Figure  5  is  a  plan 
view,  enlarged  scale,  showing  more  clearly  the  screws 
and  screw-case,  the  latter  in  section. 

"Similar  letters  of  reference  indicate  corresponding 
parte  in  all  the  figures. 

"A  A  A  are  taper  screws  or  worms;  B  B  B,  the 
screw-cases,  connected  at  the  front  of  the  boiler  by  the 
feed-trough  C,  the  latter  being  supplied  with  fuel  by 
way  of  the  hopper  E.  The  screws  AAA  are  supported 
at  one  cud  by  the  feed-trough  C,  and  by  contact  with 
I  he  bottom  of  the  screw-case. 

"  Motion  is  given  to  the  screws  A  A  A  by  means  of 
the  ratchet-wheels  FFF  and  pawls,  linked  together 
by  bar  G,  and  actuated  by  lever  IT;  or  the  three  worms 
.1  .1  A  maybe  driven  by  longitudinal  shaft-worm  and 
worm-wheels. 


222  COMBUSTION    OF    COAL. 

"  J  is  a  frame,  within  which  the  auxiliary  bars  K  are 
received,  being  free  to  tilt  on  their  axles  or  gudgeons  L 
when,  by  means  of  the  rod  M,  the  links  N  R  R  are 
operated,  so  as  to  tilt  and  thereby  discharge  the  ashes  or 
spent  fuel  from  the  bars  to  the  bottom  of  the  flue. 

"  Two  screws  may  be  put  in  one  screw-case. 

"  I  do  not  claim  as  my  invention  the  use  of  a  screw 
per  se;  but 

"  I  claim — 

"  The  combination  of  the  grate-bars  of  a  furnace 
with  the  troughs  or  tapering  screw-cases  B  B,  that  are 
placed  below  and  between,  and  communicate  with  the 
several  grate-bars,  and  connect  at  one  end  to  a  hopper, 
each  of  said  screw-cases  containing  a  tapering  screw  or 
worm,  A,  so  arranged  that  the  fuel  is  fed  by  the  screws 
or  worms  A  from  the  hopper  into  the  screw-cases  B, 
and  from  the  screw-cases  directly  upon  the  grate-bars, 
all  substantially  as  and  for  the  purpose  herein  shown 
and  described." 


M.H.SMITH. 
FURNACE    FEEDER 


FIG.  i. 


' 


CHAPTER  XIII. 

SPONTANEOUS  COMBUSTION  OF  COAL.* 

Most  Likely  to  Occur  on  Board  Ships — -Vessels  Lost  from  this 
Cause  in  1874 — Spontaneous  Combustion  Begins  in  the  Center 
of  the  Heap  or  Middle  of  the  Cargo — Iron  Pyrites  in  Coal 
— How  Carbon  Spontaneously  ignites — Coal  requires  no  Initial 
Temperature  for  its  Combustion — No  Limit  to  the  Heat  which 
may  be  Produced  by  Concentration. 

"The  most  serious  cases  of  spontaneous  combustion 
are  in  ships  carrying  coal.  These  have  of  late  been  so 
numerous,  and  have  so  often  occurred  in  despite  of 
manifold  precautions,  that  a  royal  commission  was 
recently  appointed  to  make  inquiry  into  the  causes  of 
these  terrible  catastrophes,  and  to  suggest  remedies 
which  it  may  be  possible  to  adopt  for  preventing  and 
guarding  against  them.  Numerous  board  of  trade 
inquiries  had  already  been  made  into  casualties  caused 
by  explosions  or  fires  in  coal-laden  vessels,  but  without 
any  improvement  in  the  safety  of  shipment  resulting 
therefrom,  until,  at  length,  the  board  declined  to  hold 
any  more,  for  the  reason  that  the  findings  of  their 
courts  (which  invariably  took  the  form  of  an  exonera- 
tion of  the  ship's  officers,  and  a  recommendation  in 
favor  of  Letter  ventilation)  appeared  to  be  entirely  dis- 
regarded. Loth  by  shipping  and  underwriting  interests. 

"It  was  evident,  from  this  state  of  things,  that  the 
coal   shippers  conceived  that  they   knew   more  of  the 

rlea  w.  Vincent,  P.  R.  s.  !•:.,  F.  C.  S. 


224  COMBUSTION    OF    COAL. 

causes  of  these  accidents  than  did  the  assessors  of  the 
board  of  trade.  The  Salvage  Association  thereupon 
urged  that  an  inquiry  should  be  held  by  a  commission, 
consisting  of  men  of  high  scientific  attainments,  and 
especially  acquainted  with  the  nature  of  coal  in  all  its 
conditions,  and  of  men  practically  acquainted  with  coal, 
both  at  the  pit  and  in  the  ship's  hold.  They  pointed 
out  that  the  result  might  be  to  fix,  with  a  certainty 
absolute  or  qualified,  the  causes  of  this  dangerous 
combustion,  thereby  attaching  to  proper  persons  the 
responsibility  for  due  precautions. 

"  The  commission  sat,  and  has  now  issued  its  report, 
from  which  much  valuable  information  as  to  the  nature 
of  these  disasters  can  be  obtained,  and,  to  a  certain 
extent,  modes  of  preventing  them,  though  this  part  of 
the  subject  still  requires  most  serious  consideration, 
since  at  present  the  carriage  of  coal  for  a  long  distance 
at  sea  must  be  regarded  as  hazardous,  whatever  precau- 
tions may  be  adopted. 

"At  the  commencement  of  the  inquiry,  they  were 
struck  by  the  circumstances  that  by  far  the  greater  part 
of  the  casualties  happened  on  board  ships  which  were 
on  long  voyages.  In  1874,  among  thirty-one  thousand, 
one  hundred  and  sixteen  shipments,  amounting  to 
upwards  of  thirteen  million  tons  of  coal,  the  accidents 
were  seventy.  But  of  these  shipments,  twenty-six 
thousand,  amounting  to  over  ten  million  tons,  were  to 
European  ports.  This  left  sixty  casualties  among  only 
four  thousand,  four  hundred  and  eighty-five  shipments, 
amounting  to  two  million,  eight  hundred  and  fifty-five 


SPONTANEOUS    COMBUSTION    OF    COAL.  225 

thousand,  eight  hundred  and  thirty-one  tons  of  coal,  to 
Asia,  Africa  and  America. 

"Again,  they  were  startled  to  find  that  the  propor- 
tion of  casualties  traceable  to  spontaneous  combustion 
increases,  pari  passu,  with  the  tonnage  of  the  cargoes.. 
This  becomes  still  more  apparent  when  the  European, 
trade  is  deducted. 

"  There  were  in  1874 — 

"  Two  thousand  one  hundred  and  nine  shipments; 
with  cargoes  under  five  hundred  tons,  in  which  five  cas- 
ualties occurred,  or  under  one-fourth  per  cent. 

"One  thousand  five  hundred  and  one  shipments,, 
with  cargoes  between  five  hundred  tons  and  one  thou- 
sand tons,  in  which  seventeen  casualties  occurred,  or 
over  one  per  cent. 

"Four  hundred  and  ninety  shipments,  with  cargoes; 
between  one  thousand  and  one  thousand  five  hundreds 
tons,  in  which  seventeen  casualties  occurred,  or  three- 
and  a  half  per  cent. 

"  Three  hundred  and  eight  shipments,  with  cargoes 
between  one  thousand  five  hundred  and  two  thousand 
inns,  in  which  fourteen  casualties  occurred,  or  over  four 
and  a  half  per  cent. 

"  Seventy-seven  shipments,  with  cargoes  over  two 
thousand  tons,  in  which  seven  casualties  occurred,  or 
nine  p<T  cent. 

"The   casualties   in    vessels    bound   to   San   Francisco 
were  the   mosl    remarkable.      Deducting  vessels   under 
live  hundred   tons   (in   which    no  ease  of   spontaneous 
(16) 


22G  COMBUSTION    OF    COAL. 

combustion  were  recorded)  the  returns  show  nine  cas- 
ualties out  of  fifty-four  shipments.  These  also  increase 
in  proportion  to  the  tonnage  of  the  cargoes,  till  we  find 
that,  out  of  five  ships  with  cargoes  of  over  two  thou- 
sand tons  sent  to  San  Francisco  in  1872,  two  suffered. 

"  Careful  thought  might  have  predicted  results  of 
this  kind  from  a  consideration  of  the  nature  of  the  sub- 
stance carried,  the  mode  of  carriage,  and  the  place  to 
which  it  was  going. 

"  So  long  ago  as  1852,  Graham  pointed  out  that  the 
tendency  of  coals  to  spontaneous  ignition  is  increased 
by  a  moderate  heat,  and  gave  examples.  For  instance, 
in  one  case  coal  had  taken  fire  by  being  heaped  for  a 
length  of  time  against  a  heated  wall,  the  temperature  of 
which  could  be  easily  borne  by  the  hand;  in  another, 
coals  ignited  spontaneously  after  remaining  for  a  few 
days  upon  stone  flags  covering  a  flue,  of  which  the  tem- 
perature never  rose  beyond  150°  Fahr.  Coals  thrown 
over  a  steam-pipe  ignited,  etc.  At  the  Chartered  Gas 
Works,  coals  piled  against  a  brick  wall  two  feet  thick, 
of  which  the  temperature  did  not  exceed  120°  to  140° 
Fahr.,  became  ignited.  Neither  did  it  appear  to  matter 
whether  the  coal  was  Lancashire  and  sulphurous,  or 
Wallsend  and  bituminous.  If  they  were  exposed  to 
this  very  moderate  heat  for  a  short  time  they  were  sure 
to  ignite. 

"  Coals  conveyed  through  the  tropics  are  certainly 
in  this  state  of  danger.  When  coal  takes  fire  spon- 
taneously, it  is  invariably  in  the  center  of  the  heap  of 
small  coal  at  the  foot  of  a  hatchway,  or  in  the  middle  of 


SPONTANEOUS    COMBUSTION    OF    COAL.  227 

the  cargo,  in  this  respect  resembling  the  spontaneous 
combustion  of  hay-stacks,  oily  waste,  etc.,  and  from 
hence  it  may  be  inferred  that  the  increments  of  heat 
which  cumulate  in  vivid  combustion  are  very  small, 
since  they  require  to  be  held  prisoners  by  impassable 
barriers  of  non-conducting  matter,  or  they  would  escape. 

"Coal  in  small  quantity,  and  in  a  cool  place,  never 
ignites  spontaneously,  but  it  does  not,  therefore,  follow 
that  all  the  conditions  leading  up  to  spontaneous  com- 
bustion are  absent,  but  only  that  one  of  them,  and  that 
an  all-important  one,  the  means  of  accumulating  of 
heat,  is  absent,  since  the  barriers  interposed  to  its  escape 
are  not  sufficiently  close-fitting. 

"The  large  ships  to  San  Francisco  had  to  encounter 
elevated  temperature,  and  at  the  same  time  the  coal  was 
in  great  mass;  they  were,  therefore,  much  more  liable 
to  accident  than  those  carrying  smaller  quantities,  and 
for  shorter  distances. 

"It  has  already  been  pointed  out  that,  whilst  wood 
is  living,  moderate  heat,  so  far  from  causing  its  destruc- 
tion, promotes  its  growth;  it  is  the  heat  which  disap- 
pears, not  the  plant.  When  the  wood  has  ceased  to 
live,  moderate  heat  dries  up  its  juices,  renders  it  brittle, 
ami  ultimately  causes  its  complete  disintegration,  and 
combustion  of  air  is  supplied,  though  the  process  is 
exceedingly  slow.  Some  years  ago.  the  sawdust  pack- 
ing round  a  steam  pipe  at  the  Queen's  Printing-office, 
Shacklewell,  was  found  to  be  charred.  Wooden  beams 
resting  against  hot  plates  which  never  reach  the  boiling 
point  of  water,  are  sometimes    found   to  be  charred,  but 


228  COMBUSTION    OF    COAL. 

oxygen  being  of  necessity  excluded  by  the  position  of 
the  wood,  combustion  does  not  happen. 

"At  the  ordinary  temperature  of  the  air,  oxygen  has 
so  little  action  upon  wood  that  it  is  practically  inde- 
structible. In  coal,  however,  the  wood  has  undergone 
changes  which  render  it  far  more  readily  affected  by  the 
oxygen  of  the  air  than  it  was  heretofore,  and  it  must  be 
borne  in  mind  that  if  once  a  combustion  is  sufficiently 
rapid  to  overcome  the  cooling  effect  of  currents  of  air, 
it  will  proceed  with  increased  vigor,  and  the  ignited 
coal  will  burn,  not  only  in  the  interior  of  the  cargo  or 
heap,  but  on  its  surface  also.  Knowing,  then,  that  coal, 
if  kept  in  bulk  at  a  temperature  slightly  raised  above 
the  common  is  sure  to  ignite,  the  question  still  remains, 
how  does  it  attain  the  degree  of  heat  at  which  active 
combination  can  take  place?  And  at  what  tempera- 
ture do  the  combinations  of  the  carbon  and  oxygen,  the 
hydrocarbons  and  the  oxygen,  begin  to  take  place?  In 
other  words,  what  is  the  temperature  of  the  initial  point 
of  the  combustion,  and  how  is  it  reached?  Many 
explanations  have  been  given.  The  well-known  fact 
that  heaped-up  iron  pyrites  in  shale,  when  wetted,  often 
causes  the  combustion  of  the  pile,  as  in  alum  making, 
has  been  used  as  m\  argument  against  the  shipment  of 
"brassy"  coal,  i.  £.,  coal  containing  these  pyrites.  But 
supposing  this  were  so,  and  that  the  pyrites  were  dis- 
seminated through  a  part  of  the  cargo  in  sufficient 
quantity  to  cause  evolution  of  heat  when  wetted,  this 
would  account  for  but  a  small  number  of  the  cases  of 


HOW    CARBON    SPONTANEOUSLY    IGNITES.  229 

spontaneous  combustion  of  coal,  since  by  far  the  larger 
number  happen  with  coal  free  from  pyrites. 

HOW  CARBON  SPONTANEOUSLY  IGNITES. 

"Condensation  of  oxygen,  by  carbon,  which  was 
referred  to  at  the  outset  of  this  paper,  is  a  far  more 
likely  mode  of  attaining  the  initial  temperature.  This 
is  pointed  out  by  Professor  Abel  and  Professor  Percy  in 
the  appendix  to  the  report  of  the  Royal  Commission. 
A^  already  stated,  carbon,  in  a  finely  divided  state,  lias 
the  power  of  condensing  oxygen  within  its  pores:  now, 
to  condense  a  gas.  Force  is  consumed,  and  heat  is  pro- 
duced. In  the  tire-syringe  a  piece  of  tinder  is  set  on 
fire  by  the  heat  evolved  by  the  condensation  of  the  air. 
When  charcoal  condenses  oxygen,  heat  is  liberated,  and 
if  the  charcoal  is  freshly  burned,  the  rapidity  of  the 
action  will  produce  such  an  amount  of  heat  as  to  cause 
the  chemical  combination  of  the  oxygen  and  carbon, 
when,  of  course,  combustion  takes  place  with  evolution 
of  Light  and  heat.  The  initial  temperature  of  the  action 
is  here  due  to  the  sudden  squeezing  together  of  the 
gaseous  molecules,  for  it'  the  air  be  admitted  to  the 
freshly  burned  charcoal  by  slow  degrees,  no  combustion 
takes  place. 

"The  appendix  suggests: 

"'The  tendency  to  oxidation,  which  carbon  and  car- 
bon compounds,  existing  in  such  a  substance  as  charcoal, 
possess,  is  favqred  by  the  condensation  of  oxygen  within 
its  pores,  whereby  the  very  intimate  contact  between 
the  carbon  and  oxygen  particles  is  promoted.     Hence, 


230  COMBUSTION    OF    COAL. 

the  development  of  heat,  and  the  establishment  of 
oxidation  occur  simultaneously,  the  latter  is  accelerated 
as  the  heat  accumulates,  and  chemical  action  is  thus 
promoted,  and  may,  in  course  of  time,  proceed  so  ener- 
getically that  the  carbon  or  carbo-hydrogen  particles 
may  be  heated  to  igniting  point. 

"  '  This  explanation  has  a  direct  bearing  upon  a  spon- 
taneous ignition  of  coal.  The  more  porous  and  readily 
pxidizable  portions  of  coal,  which  are  known  to  be  more 
or  less  largely  disseminated  through  seams  from  different 
localities,  undergo  oxidation  by  absorption  of  atmos- 
pheric oxygen,  and  by  the  exposure  of  large  surfaces  to 
its  action,  and  the  heat  developed  by  that  action  will 
accumulate,  under  favorable  conditions,  to  such  an 
extent  as  soon  to  hasten  the  oxidation  and  the  conse- 
quent elevation  of  temperature,  until  some  of  the  most 
finely  divided  and  readily  inflammable  portions  actually 
become  ignited."' 

"  Water  does  not  assist  in  the  spontaneous  combus- 
tion of  coal  except  where  pyrites  are  concerned.  There 
is  much  misunderstanding  as  to  the  part  played  by 
water  in  the  changes  leading  to  spontaneous  combus- 
tion. The  water  itself  is  not  decomposed,  as  some 
people  have  imagined.  The  heat  evolved  during  the 
combustion  of  hydrogen  and  oxygen,  during  the  com- 
bination to  form  water  (the  heat  of  the  oxy-hydrogen 
blow-pipe)  must  be  supplied  before  they  can  be  again 
torn  apart,  so  that,  so  far  from  water  being  a  producer 
of  heat,  it  is  likely  to  be  a  consumer. 


HOW    CARBON    SPONTANEOUSLY    IGNITES.  231 

"Moreover,  experiment  goes  to  prove  that  coal 
requires  no  initial  temperature  for  its  combustion,  and 
that  the  supposition  of  condensation  by  porous  coal, 
though  it  may  take  place,  is  unnecessary  for  its  spon- 
taneous combustion.  The  ties  holding  the  constituents 
of  coal  together,  which  in  the  living  plant  were  so 
strong  that  they  defied  the  power  of  the  sun  to  rend 
them  asunder,  have  now  become  so  weak  that  the  oxy- 
gen of  the  air,  even  when  no  hotter  than  fifty-five 
degrees  Fahr.,  can  seize  upon  and  combine  with  at  leasi 
some  of  the  carbon,  forming  carbonic  acid.  Air  blown 
through  a  tube  filled  with  coarsely  powdered  coal, 
into  baryta  water,  furnishes  a  considerable  amount  of 
barium  carbonate  in  a  very  short  time.  Other  circum- 
stances may  aid,  but  it  is  sufficient  to  prove  the  produc- 
tion of  carbonic  acid  to  make  it  certain  that  heat  is  set 
free,  and  if  escape  of  the  heat  is  barred,  it  must  accu- 
mulate, till  at  length,  it  reaches  the  point  at  which  com- 
bustion becomes  visible,  and  in  too  many  eases  uncon- 
trollable. 

••A-  there  is  no  amount  of  cold  which  may  not  he 
intensified  by  free  radiation,  so  there  is  no  limit  to  the 
lieaf  which  may  he  produced  by  concentration,  or,  in 
other  words,  by  stoppage  of  all  radiation  except  to  one 
common  point.  Siemens' admirable  regenerators  net  on 
the  principal  of  continuous  passage  of  heated  gases 
through  passages,  where  the  gases  arc  deprived  of  heal : 

when  the  heal  producers  go  forth  to  do  their  work, 
they  are  fn>t  made  to  pa8S  through  these  heated  pass- 
ages.      In   addition    t,,   their  own  proper  heat,  they  thus 


232  COMBUSTION    OF    COAL. 

convey  forward  the  stored-up  heat,  and  the  most  intense 
heat  yet  met  with  for  practical  purposes  is  attained. 

"  It  is  to  be  feared  that,  in  ventilating  the  cargoes  of 
coal-ships,  the  principle  of  Siemens'  regenerator  is 
infringed  upon,  to  the  great  damage  of  the  cargo.  Air 
is  forced  through  the  coal,  oxidation  and  heat  follow 
throughout  its  course,  the  heat  is  absorbed  by  the  coal, 
and  the  air,  as  it  is  continuously  forced  in,  passes  over 
surfaces  which  are  becoming  hotter  and  hotter,  the  air 
is  itself  heated,  and  the  work  of  combustion,  once 
begun,  goes  on  more  and  more  rapidly. 

"In  view  of  these  facts,  there  is  small  wonder  that 
the  uniform  recommendation  of  the  Board  of  Trade 
Assessors,  'to  ventilate  the  cargoes,'  should  have  met 
with  cavalier  treatment.  The  subject  is,  however,  yet 
far  from  being  fully  understood.  Evidence  has  been 
collected  from  most  trustworthy  sources,  and  a  clear 
understanding  obtained  of  the  various  conditions  under 
which  spontaneous  combustion  of  coal  takes  place. 
What  is  now  wanted  is,  a  thorough  experimental  inves- 
tigation of  the  causes  of  the  spontaneous  combustion. 
The  reasons  already  given  are  probably  correct,  but 
they  are  supported  by  the  feeblest  experimental  support, 
and  until  this  is  strengthened,  we  can  neither  speak 
with  the  necessary  boldness  in  reproving  the  actions 
which  lead  to  the  lamentable  losses  of  good  fuel,  good 
ships,  and,  but  too  often,  of  good  men;  nor  can  we 
decide  as  to  the  proper  means  for  preventing  their 
occurrence." 


CHAPTER  XIV. 

COAL-DUST  FUEL. 

Continuous  Firing — How  a  Furnace  should  be  Fed  when  Using 
Powdered  Fuel — Experiments  of  United  States  Government 
in  1876 — Comparative  Economy  of  Powdered  Fuel  as  Com- 
pared with  Ordinary  Coal — Stevenson's  Apparatus  for  Burn- 
ing Coal- Dust. 

COAL-DUST  FUEL  (8). 

When  coal  is  burned  in  large  lumps  a  certain 
amount  of  power  is  expended  in  the  furnace  in  disinte- 
grating the  fuel.  This  is,  however,  comparatively  a 
small  matter.  But  it  is  obvious  that  difficulties  are 
thrown  in  the  way  of  the  union  of  the  carbon  with  the 
oxygen  of  the  air,  and  it  has  come  to  be  recognized  as  a 
feature  of  good  stoking  that  the  coal  should  be  broken 
into  moderately  small  pieces  before  it  is  put  into  the 
furnace,  and  that  the  process  of  firing  should  be  as  con- 
tin  in >us  as  possible.  The  great  advantage  derived  from 
the  use  of  mechanical  stokers  lies  no  doubt  in  the 
almost  perfect  fulfillment  of  the  last  named  condition. 
If  we  carry  the  idea  a  little  further,  the  use  of  coal  in  a 
state  of  powder  will  suggest  itself;  and  as  it  is  impossi- 
ble to  feed  a  lire  satisfactorily  by  hand  with  coal-dust, 

it  has   come   to    be    undersl 1    that  it  should  be  blown 

into  the  furnace  with  the  air  required  lor  its  combus- 
tion, which  is  thus  intimately  mingled  with  the  carbon; 
Until  a  very  recent  period  this  system  was  only  used  by 
Mr.  Crampton,  whose  well  known  revolving  puddling 


234  COMBUSTION   OF    COAL. 

furnace  is  supplied  with  powdered  coal  by  a  fan  blast, 
the  coal  being  first  ground  very  fine  between  an  ordin- 
ary pair  of  millstones.  We  believe  that  at  one  time 
Mr.  Crampton  applied  this  system,  but  without  success, 
to  a  steam  boiler.  We  are  not  in  possession  of  any  of 
the  details  of  this  experiment,  and  so  we  can  say  noth- 
ing about  the  cause  of  failure. 

UNITED  STATES  EXPERIMENTS. 

In  1876  a  series  of  trials  were  conducted  by  the 
American  Government  to  determine  the  value  of  a  sys- 
tem of  burning  powdered  fuel,  patented  by  Messrs. 
Whelp! ey  and  Storer. 

The  boiler  was  forty  inches  in  diameter  and  ten  feet 
long;  it  was  a  plain  cylinder  externally  fired,  the  products 
of  combustion  returning  to  the  front  end  through  sev- 
enty-four tubes  two  and  one-quarter  inehes  in  diameter 
outside;  the  total  heating  was  four  hundred  and  forty- 
two  square  feet.  The  air  required  for  combustion  was 
delivered  into  the  closed  ash-pit,  vertically,  through  a  pipe 
five  inches  in  diameter.  The  powdered  coal  was  sent  in 
through  a  pipe  two  inches  in  diameter,  arranged  hori- 
zontally. The  boiler  was  tried  both  with  powdered  an- 
thracite and  lump  anthracite,  the  only  change  made  as 
regards  the  boiler  consisting  in  the  removal  of  a  brick 
arch  used  with  the  dust  fuel.  This  increased  the  heating 
surface  to  four  hundred  and  fifty-seven  square  feet.  Each 
experiment  lasted  forty-eight  hours.  Four  experiments 
were  made;  two  with  lump  coal  alone,  and  two  with 
lump  coal  supplemented  by  dust  coal  below  or  above  it. 


COAL-DUST    FUEL.  235 


"Results  of  Experiments — Calling  the  experiments 
with  lump  coal  alone  A,  and  those  with  dust  coal  C 
and  D,  the  results  may  be  briefly  stated  as  follows: 
In  experiment  A,  11.113  pounds  of  lump  coal  were 
consumed  per  hour  per  square  foot  of  grate  surface, 
with  80.478  double  strokes  of  the  piston  of  the  engine 
supplying  air;  the  resulting  vaporization  per  pound  of 
the  combustible  portion  of  the  coal  was  10.124  pounds 
of  water  from  the  temperature  of  two  hundred  and 
twelve  degrees  Fahrenheit,  and  under  the  atmospheric 
pressure.  The  mean  rate  of  combustion  in  experi- 
ments C  and  D  was  11.350  pounds  of  the  combustible 
portion  of  the  coal  consumed  per  hour  per  square 
foot  of  grate  surface,  with  79.748  double  strokes  per 
minute  of  the  piston  of  the  engine  supplying  air,  the 
resulting  vaporization  per  pound  of  the  combustible 
portion  of  the  coal  being  10.192  pounds  of  water  from 
the  temperature  of  two  hundred  and  twelve  degrees 
Fahrenheit,  and  under  the  atmospheric  pressure.  The 
two  economic  results — namely,  10.124  and  10.192 — are 
almost  identical,  and  show,  when  scnii-bituminous  coal 
is  burned  at  the  same  rate  of  combustion,  with  the  same 
pro  rut"  air  admission,  and  under  the  same  circum- 
stances, it  gives  the  same  economic  vaporization, 
whether  it  is  consumed  wholly  in  the  lump  state,  or 
partly  in  the  lump  and  partly  in  the  pulverized  state, 
or  wholly  in  the  pulverized  state.  The  equality  of 
economic  result  is  also  proved  by  the  fact  of  the 
equality  of  the  temperature  of  the  gases  of  combustion 
in  the  comparable  experiments  when   leaving  the  boiler. 


236  COMBUSTION    OF    COAL. 

In  experiment  A,  burning  lump  coal  alone,  this  temper- 
ature was  383.30  degrees  Fahrenheit,  while  the  mean  of 
the  temperature  of  the  gases  of  combustion  in  the 
boiler-uptake  during  experiments  C  and  D,  during 
which  partly  lump  coal  and  partly  pulverized  coal 
were  consumed,  was  381.85  degrees  Fahrenheit.  This 
comparison  is  made,  however,  for  the  heating  effects 
alone  of  the  coal  in  the  two  states,  burned  under  the 
same  circumstances,  and  is  exclusive  of  the  cost  in  fuel 
of  pulverizing  the  coal,  and  of  blowing  the  dust  into 
the  furnace.  A  correct  commercial  comparison  must 
include  this  cost,  which  is  only  incurred  when  the  coal 
is  used  in  the  pulverized  state,  because  when  it  is  used 
in  the  lump  state  it  can  be  burned  as  rapidly  with  the 
natural  draught  as  the  pulverized  coal  can  with  the 
artificial  draught  obtained  by  the  fan-blowers.  The 
reason  why  the  pulverized  coal  can  not  be  consumed  at 
a  greater  rate  with  the  fan-blowers  than  the  lump  coal 
can  be  consumed  with  the  average  draught  given  by 
the  boiler  chimney  is,  that  the  former  requires  a  certain 
time  for  ignition  and  combustion,  which  is  much  longer 
than  the  latter  requires,  because  the  temperature  to 
which  the  former  is  exposed  above  the  bed  of  incandes- 
cent fuel  on  the  grate-bars  is  much  less  than  the  tem- 
perature of  that  bed  to  which  the  latter  is  exposed. 

"The  cost  of  the  net  horse-power  in  average  practice 
may  be  taken  at  about  four  pounds  of  coal  per  hour. 
Now,  the  mean  of  experiments  C  and  D  gave  1.381  net 
horse-power  developed  by  the  engine  in  pulverizing  the 
coal,  and  in  blowing  the  dust  into  the  furnace,  and  in 


COAL-DUST    FUEL.  237 


pumping  the  feed-water  into  the  tank,  which,  at  four 
pounds  of  coal  per  hour  per  horse-power,  is  5.524 
pounds  of  coal  per  hour,  or,  as  the  coal  consumed  per 
hour  was  66  pounds,  8.37  per  cent,  of  the  total  weight 
of  coal  burned.  Consequently,  the  pulverized  coal  was 
commercially  8.37  per  cent,  inferior  to  the  lump  coal. 
In  experiment  A,  during  which  lump  coal  was  burned 
alone,  there  was  required  to  drive  the  fan-blowers  and 
to  pump  the  feed-water  0.500  net  horse  power,  which,  at 
four  pounds  of  coal  per  hour  per  horse-power,  required 
2.000  pounds  of  coal  per  hour  to  produce  it,  and  as  the 
hourly  consumption  of  coal  during  that  experiment  was 
66  pounds,  there  were  consumed  in  producing  the  artin- 
eial  draught  and  in  pumping  the  feed-water  3.06  per 
cent,  of  the  total  weight  of  coal  burned.  Deducting 
this  3.06  per  cent,  from  the  8.37  per  cent.,  as  given  in 
the  immediately  preceding  paragraph,  there  remains 
5.31  per  cent,  of  the  total  weight  of  coal  consumed, 
applied  to  the  pulverization  of  the  coal  alone.* 

"From  this  it  will  be  seen  that  the  use  of  powdered 
fuel  was  more  expensive  than  that  of  lump  coal,  about 
in  the  ratio  of  the  cost  of  pulverization,  and  so  far  the 
scheme  was  a  failure.  As  regards  the  details  of  the 
apparatus  used  our  information  is  meagre.  Mr.  13.  F. 
[sherwood,  by  whom  the  experiment  was  made,  thus 
comments  on  it  :  'The  lump  coal  is  first  reduced  by  a 
patented  apparatus  (which  is  the  only  portion  of  Messrs. 
Whelpley  and  Storer's  process  that  is  patented  or  patent- 

Ainm..i   Report  of  the  Chief  of  the   United  States  Bureau  "i   Steam  En- 
gineers foi  1876 


238  COMBUSTION    OF    COAL. 

able)  to  the  state  of  impalpable  powder,  and  it  is  then 
fed,  together  with  air,  through  a  conduit  to  the  central 
portion  of  an  ordinary  centrifugal  or  fan-blower,  whose 
revolutions  draw  it  in  and  drive  it  through  another 
conduit,  which  discharges  it  into  the  front  of  the  furnace 
through  an  air-tight  aperture.  The  lump  coal  is  fired 
in  the  usual  manner,  through  the  furnace-door,  and  the 
air  for  its  combustion  is  supplied  by  another  fan-blower 
delivering  into  a  closed  ash-pit  beneath  the  grate-bars. 
The  whole  combustion  is,  therefore,  effected  by  artificial 
draught  depending  on  mechanism ;  and  the  force  of  this 
draught  is  easily  regulated  from  the  least  to  the  greatest 
desirable  in  burning  coal ;  it  can  also  be  distributed  at 
will,  so  as  to  preserve  within  certain  limits  any  required 
proportion  between  the  weights  of  lump  and  dust  coal 
consumed  in  the  same  time.  The  two  fan-blowers,  in 
the  experiments  described,  were  operated  by  the  same 
steam  engine  which  effected  the  coal-crushing  and 
worked  the  feed-pump  of  the  boiler. 

Why  the  Experiments  were  made  — "  The  patentees 
imagine  that,  compared  with  the  combustion  of  lump 
coal,  a  more  nearly  perfect  combustion  was  to  be 
obtained  with  impalpably  fine  coal-dust  mixed  throughly 
with  and  suspended  in  air,  thereby  presenting  to  the 
latter,  for  a  given  weight  of  coal,  an  immensely  greater 
surface  than  in  the  lump  state.  They  imagined,  too, 
that,  from  the  same  cause,  a  much  higher  rate  of  com- 
bustion would  be  obtained  than  was  probable  with 
lump  coal,  by  which  means  a  boiler  with  a  much  smaller 
grate-surface,  but  with  the  same  heating  surface,  would 


stevensox's  apparatus.  239 

furnish  with  the  coal-dust  the  same  quantity  of  steam. 
in  equal  time,  and  with  greater  economy  of  evaporation 
per  pound  of  fuel  than  with  the  lump  coal.  It  was  to 
determine  the  truth  or  error  of  these  assumptions  that 
the  experiments  were  made.  They  Avere  intended  to 
have  been  very  extensive,  embracing  anthracite  and 
coke,  as  well  as  bituminous  and  semi-bituminous  coals; 
and  also  a  species  of  exceedingly  hard  anthracite,  found 
in  Rhode  Island,  which  contains  about  forty  per  centum 
of  incombustible  mineral  matter,  and  is  worthless,  from 
its  difficulty  of  ignition  and  slowness  of  combustion,  for 
burning  in  lumps.  The  results  from  different  rates  of 
combustion  and  different  proportions  of  dust,  to  lump 
coal  consumed  in  equal  time,  were  likewise  to  have 
been  ascertained,  but  the  experiments  were  prematurely 
closed,  as  the  government  could  not  longer  dispense 
with  the  services  of  the  naval  engineers  making  them. 

"The  obvious  defects  of  the  scheme  were,  that  the 
coal  could  not  be  burned  fast  enough,  and  it  is  instruc- 
tive to  note  that  the  cooling  down  of  the  furnace  of  the 
boiler  was  one  principal  factor  in  bringing  about  this 
result." 

STEVENSON'S  A  I'l'A  KA'I  i  S. 

Plate  I V  is  a  representation  of  the  apparatus  for 
burning  coal-dust,  the  invention  of  Mr.  G.  K.  Stev- 
enson, of  Valparaiso,  and  which  lias  been  at  work  in 
Wellington  street,  Blackfriars,  London.  This  appara- 
tus overcomes,  it  would  appear,  the  objections  urged 
against  Messrs.  WTielpley  and  Storer's  plan,  and  de- 
serves   attention    from    engineers.      The   apparatus  is 


240  COMBUSTION   OF   COAL. 

illustrated  in  the  accompanying  engravings,  and  may 
be  briefly  described  as  follows:  The  boiler  used  is 
one  of  two  precisely  alike,  placed  side  by  side,  as 
shown.  They  are  Cornish  boilers,  with  a  single  flue 
in  each,  and  are  of  the  dimensions  shown  in  the  draw- 
ing. Confining  our  attention  to  that  to  which  Mr. 
Stevenson's  invention  is  affixed,  it  will  be  seen  that  the 
grate-bars  are  removed,  and  in  the  furnace  is  placed  a 
species  of  fire-clay  retort,  the  sides  of  which  are  perfor- 
ated with  numerous  holes,  about  a  half  inch  in  diam- 
eter. The  air  and  powdered  fuel  are  driven  in  together 
through  the  pipe  J5,  which  is  six  inches  in  diameter.  A 
few  fire-bricks  are  arranged  in  the  flue,  behind  the 
retort,  to  act  as  a  bridge. 

"  The  coal  is  reduced  to  a  fine  powder  by  a  -small 
disintegrator,  which  delivers  into  a  closed  sheet  iron 
tank  to  prevent  the  escape  of  dust.  It  is  brought  to 
the  condition  of  a  somewhat  coarse  powder,  and  is  not 
impalpable.  The  appliances  in  use  in  Wellington  street 
are,  in  many  respects,  makeshift,  and  the  powdered  fuel 
is  conveyed  by  hand  to  a  hopper,  E,  figure  2.  In  the 
base  of  this  hopper  is  a  small  delivery  wheel,  C,  in  the 
rim  of  which  are  notches  c  c.  These  notches  are  pro- 
vided with  slides  worked  by  a  very  simple  arrangement, 
which  compels  them  to  obey  the  action  of  gravity  and 
fall  to  the  bottom  of  the  notches  when  they  are  at  the 
top  of  the  wheel  C.  The  notches  then  fill  with  coal- 
dust,  and,  as  the  wheel  revolves,  the  slides,  being  thrust 
downward,  push  the  coal  out  of  the  notches  into  the 
air  tunnel  B  B.     The  rate  of  deliverv  of  the  coal  can 


steyenson's  apparatus.  241 

thus  be  accurately  fixed  by  regulating  the  speed  of  the 
wheel  C,  which  is  driven  by  a  face  friction  wheel,  in  a 
way  that  will  be  readily  understood.  By  setting  the 
friction  wheel  nearer  or  further  from  the  axis  of  (',  the 
speed  of  the  latter  can  be  altered  without  affecting-  that 
of  any  other  portion  of  the  apparatus.  In  order  to  mix 
the  coal-dust  with  the  air,  a  twisted  plate  of  metal,  g  gT 
is  put  in  the  air  tunnel.  This  causes  a  rotary  motion  in 
the  current,  and  produces  the  required  effect.  B  B  is. 
prolonged  into  the  firing  place,  and  coupled  on  to  the 
pipe  B,  figure  one,  by  a  socket.  The  air  is  supplied  by 
a  blower  A  A,  figure  two,  driven  by  a  belt  from  a  lay- 
shaft.  The  apparatus  is  started  by  lighting  a  fire  in  the 
retort  A,  figure  one.  After  this  has  burned  up,  if  steam 
be  available,  the  blower  is  set  in  motion  and  coal-dust 
and  air  i'vd  into  the  retort,  the  front  of  which  is  bricked 
up,  as  shown  in  the  end  view  of  the  boiler,  figure  three. 
"Several  experiments  have  been  carried  out  to  test 
the  value  of  the  apparatus.  One  by  Mr.  T.  B.  Jordan. 
of  Queen  Victoria  street,  lasted  five  hours  and  fifty-five 
minutes.  The  boiler  evaporated  5984  pounds  of  water 
from  eighty-one  degrees  with  720  pounds  of  coal,  or 
8.312  pounds  per  pound  of  coal.  In  a  previous  experi- 
ment, lasting  live  hours,  the  same  boiler,  fired  in 
the  ordinary  way,  evaporated  10.194  pounds  of  water 
with  1568  pounds  of  coal,  or  at  the  rate  of  (J. 501 
pounds  per  pound  of  coal.  In  a  third  experiment, 
made  by  Mr.  (?.  Barker,  of  Birmingham,  the  trial 
lasting    live    hours   and    fifty-five   minutes,    720  pounds 


242  COMBUSTION    OF    COAL. 

of  coal  were  burned,  and  evaporated  5984  pounds  of 
water,  or  at  the  rate  of  8.312  pounds  per  pound  of 
coal  from  fuel  at  eighty-one  degrees,  the  pressure  being 
forty-two  and  one-half  pounds.  In  an  experiment  with 
the  same  boiler,  hand  fired,  the  evaporation  was  6.5 
pounds  per  pound  of  coal. 

"  More  recently  we  carried  out  ourselves  an  experi- 
ment which  lasted  two  hours.  The  boiler  was  filled  up 
to  begin  with,  and  the  experiment  commenced  when 
the  pressure  was  44  pounds.  During  the  run  no  water 
was  fed  into  the  boiler  After  it  was  over  the  donkey 
was  started  and  the  boiler  pumped  up  to  the  same  level 
as  at  starting.  The  stop- valve  being  closed,  the  press- 
ure rose,  notwithstanding  the  feed — a  result  due  to  the 
intense  heat  of  the  clay  retort  and  fire-bricks.  The 
whole  quantity  evaporated  was  thirty-five  cubic  feet,  or 
twenty-one  hundred  and  eighty-four  pounds.  The 
weight  of  coal  burned  was  176.5  pounds,  and  it  follows 
that  12.3  pounds  of  water  per  pound  of  coal  were  evap- 
orated from  and  at  a  temperature  of  two  hundred  and 
ninety-one  degrees.  It  will  be  seen  that  the  rate  of 
evaporation  was  extremely  low  for  so  large  a  boiler,  and 
it  is  proper  to  add  that  the  blower,  which  ran  at  an 
average  speed  of  two  hundred  and  sixty  revolutions  per 
minute,  was  driven  by  a  lay-shaft  running  too  slowly, 
but  over  which  Mr.  Stevenson  had  no  control.  The 
speed  also  varied  considerably,  which  was  against  the 
performance  of  the  apparatus.  Throughout  everything 
worked  perfectly  without  a  hitch  or  difficulty  of  any 


Plate   IV 


STKVENSo.VS  A  IM'A  RATU8   FOR    BURNING    POWDERED  FUEL. 


stevexson's  apparatus.  243 

kind;  and  the  closing  of  the  boiler  front  rendered  the 
firing  place  exceedingly  cool — a  manifest  advantage. 

A  curious  feature  of  Air.  Stevenson's  apparatus  is, 
that  the  quantity  of  air  admitted  per  pound  of  coal 
admits  of  accurate  determination.  During  the  trial,  at 
which  we  were  present,  the  blower  supplied  1.2  cubic 
feet  of  air  per  revolution.  This  was  determined  by 
measuring  the  capacity  of  the  blower,  and  checking  the 
result  with  a  delicate  anemometer,  placed  at  the  mouth 
of  the  coal  delivery  pipe,  the  coal  being  shut  off.  ISTow 
1.2X260=312  cubic  feet,  or  twenty-four  pounds  of 
air  per  minute.  The  coal  supplied  in  the  same  time 
was  two  pounds  nearly.  Thus  only  twelve  pounds,  or 
the  least  possible  quantity  of  air  which  will  suffice  for 
combustion,  were  supplied.  Yet  there  can  be  no  doubt 
that  no  smoke  was  produced,  nor  does  it  appear  possi- 
ble that  any  coal-dust  was  deposited  unconsumed  in  the 
flues. 

We  have  endeavored  to  place  our  readers  in  posses- 
sion of  all  the  available  information  concerning  a  new 
ami  important  branch  of  physical  inquiry.  It  can  be 
easily  shown  that  in  theory,  at  all  events,  the  combus- 
tion (,t'  fuels  in  the  form  of  dust  ought  to  be  attended 
with  excellent  results;  and  Mr.  Stevenson  proved  that 
an  apparatus  can  be  made  which  will  work  without 
giving  any  trouble,  and  which  is  inexpensive  and  sim- 
ple.  lint  we  have,  on  the  other  hand,  no  data  concern- 
ing the  cost  of  breaking  the  fuel,  ami  the  apparatus  is 
quite  too  small,  or  at  least  is  run  too  slowly,  to  enable 
any  estimate  of  its  value  to  be  formed   which  can  be 


244  COMBUSTION   OF    COAL.  v 

based  on  fact  and  not  on  conjecture.  The  retort  used 
by  Mr.  Stevenson  is  far  too  small,  and  consequently 
does  not  fit  the  flue  properly. 

The  retort  must  reduce  the  efficiency  of  the  heating- 
surface  to  some  extent,  as  it  is  certainly  not  as  hot  as  a 
furnace  would  be. 

It  appears  to  be  proved  by  the  facts  which  we  have 
placed  before  our  readers,  that  a  retort,  or  its  equiva- 
lent, can  not  be  dispensed  with,  and  it  is  shown  that  a 
chemical  equivalent  of  air  will  suffice  to  produce  com- 
bustion without  smoke.  This  last  is  an  important  fact, 
and  would,  standing  alone,  entitle  the  invention  of  Mr. 
Stevenson  to  consideration. 


CHAPTER   XV. 

LIQUID  FUEL. 

Analysis  of  Crude  Petroleum — Quantity  of  Air  Required  to  Burn 
Oil — LTnits  of  Heat  Evolved  by  the  Combustion  of  Oil — Evap- 
orative Power  of  Crude  Oil — What  is  Claimed  for  Petroleum  as 
a  Fuel — Wise,  Field  and  Aydon's  System  of  Burning  Liquid 
Fuel — Extraordinary  Results  Obtained — Advantages  Arising 
from  its  Use  on  board  Steamships  and  Vessels  of  War. 

Petroleum  is  a  natural  hydrocarbon  oil.  That  of 
Pennsylvania,  from  whence  most  of  the  American  petro- 
leum is  shipped,  is  of  a  dark  brown  color,  having  a 
greenish  tinge.  In  specific  gravity  it  averages  about 
0.8,  though  it  varies  some  .025  on  either  side  of  this 
figure.  As  there  is  apparently  no  end  to  hydrocarbon 
combinations,  the  analysis  of  crude  petroleum,  as  deter- 
mined by  Professor  H.  "Wurtz,  will  be  given  as  best 
suited  to  our  present  purpose,  which  is  as  follows: 

( Jarbon 84 

Hydrogen 14 

Oxygen - 

100 

Deducting  the  oxygen  and  the  quantity  of  hydrogen 
to  form  water,  we  have 

2-h8=  .21  =  useless  hydrogen. 


246  COMBUSTION    OF    COAL. 

Then, 

14  —  .25  =  13.75  available  hydrogen, 

and 

2  +  .25  =  2.25  water, 

or 

Carbon  84 

Hydrogen 13.75 

Water 2.25 

100 

The  net  theoretical  quantity  of  air  required  to  burn 
the  carbon  to  carbonic  acid,  and  the  hydrogen  to  water, 
in  the  above  composition,  would  be, 

.84      X  12  =  10.08  pounds  of  air  for  the  carbon. 
.1375  X  95=   4.36  pounds  of  air  for  the  hydrogen. 

The  total  estimated  quantity  of  heat  that  can  be 
given  off,  by  the  complete  combustion  of  the  above, 
would  be, 

Carbon 84      X  14,544  =  12,217 

Hydrogen 1375X62,032=   8,529 

20,746  units  of  heat. 

The  theoretical  evaporative  power,  or  the  number  of 
pounds  of  water  which  may  be  evaporated  at  212°,  and 
at  atmospheric  pressure,  by  one  pound  of  oil,  as  above, 
and  containing  twenty  thousand  seven  hundred  and 
forty-six  heat  units,  the  feed  water  being  supplied  the 
boiler  at  80°  Fahr.,  may  be  determined  as  follows : 

212°  —  80°  =  132°  difference  in  temperature. 
966  +  132  =  1098 


LIQUID    FUEL.  247 


Then, 


Y^gg  =  18.89  pounds  of  water. 


The  total  equivalent  evaporative  power  of  one 
pound  of  oil,  as  above,  from  and  at  a  temperature  of 
212°  Fahrenheit,  and  at  atmospheric  pressure  is, 

„'g-  21.4/  pounds  of  water. 

Ill  these  several  calculations  the  whole  of  the  car- 
bon, and  the  excess  of  hydrogen  only,  have  been  used. 
The  whole  of  the  oxygen  and  the  combining  weight  of 
hydrogen  to  form  water  have  been  deducted  from  the 
total  analysis.  It  is  probable  that  the  figures  given 
above  represent  a  fair  average  of  the  total  heating 
power  of  crude  oil.  The  writer  is  not  aware  that  any 
calorimeter  tests  of  crude  American  petroleum  have 
been  made. 

It  is  claimed  for  petroleum  that,  on  account  of  its 
superior  heating  power,  a  sensible  reduction  in  the  size 
of  steam  boilers  may  be  made  under  that  required  for 
coal,  or,  the  boiler  remaining  the  same,  more  water  may 
be  evaporated,  and  thus  its  capacity  increased.  So  little 
is  known,  however,  of  the  actual  economic  efficiency  of 
liquid  fuel  over  coal,  under  all  conditions,  that  the  best 
form  of  furnace,  and  best  design  for  the  boiler,  can 
hardly  be  said  to  have  been  practically  determined. 

It  certainly  has  cleanliness  in  its  favor,  as  there  are 
qo  ashes  or  clinkers  left  in  the  furnace.  It  also  permits 
of  continuous  tiring  in  a  closed  furnace,  fre*e  from  drafts 
ofcoldair.    The  quantity  of  heal  required  to  maintain  a 


248 


COMBUSTION   OF    COAL. 


constant  pressure  of  steam  may  be  controlled  by  the 
simple  adjustment  of  a  valve  in  the  oil  supply  pipe.  It 
is  obvious  that  by  this  method  of  firing,  one  man  may 
attend  a  number  of  furnaces,  and  thus  dispense  with 
firemen,  coal  heavers,  and  other  attendants. 


Figure  9. 


Several  years  ago  (1868)  Messrs.  Wise,  Field  and 
Aydon's  system  of  burning  liquid  fuel  was  illustrated 
and  described  in  the  "Engineering."  The  evaporation 
reported  as  having  been  obtained  in  actual  practice  is  so 
near  the  theoretical  calorific  power  of  the  fuel,  that  it- 
seems  almost  impossible  to  improve  upon  a  process 
yielding  such  high  results.  The  engravings,  figures  9 
and  10,  show  its  application  to  a  Cornish  boiler;  these 


LIQUID    FUEL. 


>49 


engravings,  together  with  the  descriptive  matter  accom- 
panying them,  are  reproduced  from  the  above  journal: 
"As  will  be  seeu  from  the  engravings,  the  apparatus 
is  a  very  simple  character.  It  consists,  in  fact,  merely 
of   a   super-heater  arranged   as   shown,  and   a  kind  of 


Figure  10. 


injector  placed  in  an  inclined  position  just  above  the 
lire-door.  The  petroleum,  or  other  liquid  hydrocarbon, 
to  be  burnt,  is  led  to  the  injector  through  a  pipe  fur- 
nished with  a  cock,  by  which  the  supply  can  be  regu- 
lated, and  it  la  there  mel  by  the  steam  which  has  passed 
through  the  Buper-heater,  and  which  lias  thus  had  its 
temperature  raised  to  about  six  hundred  degrees.     The 


250  COMBUSTION   OF    COAL. 

injector  is  very  similar  in  its  construction  to  Gilford's 
well-known  instrument,  and  its  action  is  sucli  that  the 
liquid  fuel  is  injected  into  the  furnace  in  the  form  of  an 
exceedingly  fine  spray  mixed  with  the  super-heated 
steam.  In  the  case  of  the  arrangement  shown  in  figure 
9  the  spray  thus  injected  comes  in  contact  with  the 
hot  ashes  on  the  fire-bars,  and  is  thus  ignited ;  a  com- 
bustion ensues  which  is  very  perfect,  and  which  is  under 
most  complete  control,  the  amount  of  flame  being  read- 
ily increased  or  diminished  by  regulating  the  quantities 
of  liquid  fuel  and  steam  admitted  to  the  injector.  The 
air  necessary  to  support  combustion  is  admitted  through 
openings  in  the  fire-door,  and  so  long  as  the  apparatus 
receives  the  most  ordinary  amount  of  attention,  the 
flame  produced  is  perfectly  smokeless. 

"As  the  liquid  fuel  is  injected  by  the  aid  of  super- 
heated steam,  it  is  evident  that  a  supply  of  steam  must 
be  obtained  before  the  apparatus  can  be  brought  into 
action.  This  being  the  case,  the  arrangement  shown  by 
figure  9  will  in  many  instances  be  that  which  it  will 
be  most  convenient  to  adopt.  In  this  arrangement  the 
fire-bars  are  retained,  and  steam  can  thus  be  got  up  by 
an  ordinary  fire  in  the  usual  way.  So  soon  as  a  certain 
pressure  of  steam  has  been  obtained,  the  ordinary  fire 
can  be  allowed  to  die  out  and  the  injector  brought  into 
action,  the  ashes  remaining  from  the  ordinary  fire  serv- 
ing to  close  the  openings  between  the  grate-bars  and  to 
ignite  the  spray  of  liquid  fuel,  as  we  have  already 
explained.  This  arrangement  is  also  convenient  in  cases 
where  the  boiler  is  worked  sometimes  with  liquid  fuel 


LIQUID    FUEL.  251 


and  sometimes  with  coal.  In  this  case,  the  steam  for 
injecting  the  liquid  fuel  may  be  obtained  at  starting 
from  a  small  auxiliary  boiler  heated  by  an  ordinary  fire, 
it  being,  of  course,  merely  necessary  to  use  this  auxiliary 
boiler  until  steam  has  been  raised  in  the  main  ones. 

"Altogether  the  apparatus  here  described  is  the 
most  simple  and  efficient  that  we  have  yet  seen  for 
burning  liquid  hydrocarbons.  We  have  been  informed, 
on  what  we  consider  reliable  authority,  that  at  Mr. 
W.  C.  Barnes'  chemical  factory  at  Hackney  Wick, 
where  his  apparatus  has  been  for  some  time  at  work, 
15,240  pounds  of  water  have  been  evaporated  in  five 
hours  by  one  of  the  boilers,  by  the  consumption  of 
eight  hundred  pounds  of  oil ;  or  an  evaporation  of  nine- 
teen pounds  of  water  per  pound  of  oil.  Taking  into 
consideration  that  the  pressure  at  which  the  boiler  is 
worked  is  twenty-eight  pounds,  and  that  the  tempera- 
ture of  the  feed-water  was  66°,  this  performance  is 
equivalent  to  the  evaporation  at  atmospheric  pressure, 
from  a  temperature  of  212°,  of  twenty- two  pounds  of 
water  per  pound  of  oil  burnt.  The  fuel  used  is  the 
waste  product  left  from  coal  tar  after  the  removal  by 
distillation  of  the  naphtha  and  light  oils.  It  weighs 
about  sixty-five  pounds  per  cubic  foot,  and  is  a  refuse 
mat.  rial  produced  at  the  above  factory.  The  apparatus 
i-  Blipplied  with  oil  from  a  tank,  which  is  in  its  turn  fed 
from  the  upper  part  of  another  tank  placed  at  a  slightly 
higher  level.  This  latter  tank  has  a  funnel-shaped  bot- 
tom which  receives  the  dirt  or  other  heavy  impurities 
deposited  by  the  oil,  a  pipe  being  fitted  to  the  lowest  point 


252  COMBUSTION   OF    COAL. 

of  the  bottom,  so  that  these  impurities  can  be  drawn 
off  when  necessary.  The  oil  tank  is  also  fitted  with  a 
coiled  pipe  through  which  steam  can  be  blown  in  cold 
weather,  or  at  other  times  if  it  should  be  necessary,  to 
liquefy  the  oil.  We  have  ourselves  seen  the  apparatus 
in  action  at  Mr.  W.  C.  Barnes'  factory,  and  can  testify 
to  the  perfect  combustion  obtained  by  its  use.  It  has 
also,  we  may  mention,  been  applied,  amongst  other 
places,  to  the  boiler  of  a  steam  launch  now  at  Woolwich 
dockyard,  and  we  understand  that  it  has  in  this  case 
proved  equally  successful. 

"  The  question  of  to  what  extent  liquid  fuel  can  be 
economically  substituted  for  coal,  is  one  to  which  it  is 
at  the  present  moment  very  difficult  to  give  even  a 
general  reply,  whilst  to  give  a  precise  answer  is,  of 
course,  impossible.  The  question  is,  in  fact,  one  upon 
which  most  persons  proposing  to  use  liquid  fuel  would 
have  to  decide  for  themselves.  In  every  case  the  answer 
will  depend  greatly  upon  the  comparative  prices  at 
which  coal  and  liquid  fuel  can  be  obtained,  and  upon 
the  certainty  with  which  a  supply  of  the  latter  fuel  is 
procurable.  In  many  instances  the  rate  of  evaporation, 
which  we  have  above  mentioned  as  having  been  obtained 
at  Mr.  W.  C.  Barnes'  works,  would  be  amply  sufficient 
to  justify  the  substitution  of  liquid  fuel  for  coal,  particu- 
larly where  the  fuel  is  obtainable  in  sufficient  quantities 
close  at  hand  as  a  waste  product ;  whilst  in  other  cases, 
where  coal  can  be  got  at  a  very  cheap  rate,  this  latter 
fuel  will  have  the  advantage.  Perhaps  the  nearest 
approach  to  a  general  answer  which  can  be  given  to  the 


LIQUID    FUEL.  253 


question  is,  that  so  long  as  the  cost  of  a  certain  quantity 
of  liquid  fuel  does  not  exceed,  or  only  very  slightly 
exceeds,  the  cost  of  the  amount  of  coal  or  other  solid  fuel 
necessary  for  doing  the  same  work,  there  is  an  advan- 
tage in  using  the  liquid  fuel,  there  being  a  saving 
effected  in  the  wear  and  tear  of  fire-bars,  etc.,  and  the 
cost  of  labor  for  firing  being  very  greatly  reduced. 

"  So  far  we  have  only  been  speaking  of  land  boilers. 
In  the  case  of  steamships,  and  particularly  of  war  ves- 
sels, or  steam  yachts,  the  power  of  carrying  fuel  for  an 
increased  number  of  days'  consumption  is  one  which, 
in  many  instances,  will  outweigh  all  questions  of  cost. 
In  hot  climates,  also,  the  adoption  of  liquid  fuel  would 
materially  add  to  the  comfort  of  the  stokers,  as  in  cases 
where  it  was  used  it  would  be  comparatively  easy  to 
maintain  the  stokehole  at  a  moderate  temperature. 
Another  point,  which  is  of  importance  in  the  case  of 
both  land  and  marine  boilers  is,  that  it  appears  certain, 
from  the  experiments  which  have  already  been  made, 
that  a  greater  duty  can  be  got  out  of  any  given  boiler 
when  it  is  worked  with  liquid,  than  when  it  is  worked 
with  solid  fuel;  or,  in  other  words,  that  with  a  given 
boiler  a  much  greater  quantity  of  water  can  be  evapor- 
ated in  a  given  time  with  the  former  fuel  than  with  the 
latter." 


CHAPTER  XVI. 

GASEOUS  FUEL. 

Loss  Attending  the  Use  of  Solid  Fuels — Advantages  Connected 
with  the  Use  of  a  Gas-Fuel  —  Coal-Gas  for  Domestic  Use — 
Water-Gas — Volume  of  Water- Gas  Obtained  for  One  Ton 
of  Coal  Burned  —  Strong's  Process  for  Generating  Fuel- 
Gas  —  Professor  Gruner  Quoted  on  the  Great  Waste  of 
Heat  in  Several  Metallurgical  Processes — Comparison  between 
the  Efficiency  of  Crude -Coal  and  Water -Gas — Calorific  Inten- 
sity of  Water-Gas — Analysis  of  Water-Gas — Calorific  Equiva- 
lent of  Water -Gas — Flame  Temperature — Economic  Value  of 
Water -Gas — Influence  of  the  Specific  Heat  of  the  Products  of 
Combustion  of  Water- Gas — Water-Gas  as  an  Illuminating 
Agent — Objections  to  Water-Gas. 

There  is  always  a  loss  attending  the  generation  of 
heat  from  solid  carbonaceous  fuels,  and  perhaps  quite 
as  much  more  heat  is  lost  in  its  application  to  any 
economic  use.  The  loss  is  greater  in  proportion  as  the 
amount  of  coal  burnt  becomes  less  in  quantity.  Per- 
haps there  is  no  single  application  of  heat  in  which  the 
loss  is  greater  than  that  applied  to  the  melting  of  met- 
als in  crucibles.  In  this  metallurgical  operation  the 
fire  is  often  large,  and  urged  to  its  utmost  intensity, 
until  the  metal  has  reached  the  proper  degree  of  fusion, 
when  the  crucible  is  removed  and  the  fire  abandoned. 
This  will  apply  in  almost  any  case  where  an  intense 
heat  is  required,  and  its  use  confined  to  certain  fixed  or 
arbitrary  working  hours.  In  this  respect  liquid  or  gas- 
eous fuels  have  an  advantage  over  solid  fuels,  as  they 
need  not  be  lighted  until  the  last  moment,  the  nature  of 


GASEOUS    FUEL.  255 


the  fuel  permitting  a  concentration  of  heat  at  any 
desired  point  of  application,  and  in  any  degree  of  inten- 
sity; it  is  also,  at  all  times,  under  perfect  control,  and 
the  supply  may  he  instantly  cut  oft"  when  no  longer 
required. 

"Another  cause  of  loss  in  the  burning  of  crude  fuels, 
and  one  of  sufficient  importance  to  deserve  mention,  is 
the  fact  that  there  is  mixed  with  the  carbon  a  con- 
siderable quantity  of  foreign  matter  not  combustible, 
which  absorbs  heat  and  gives  no  equivalent.  This  is 
represented  principally  by  the  ash  and  clinker,  which 
every  consumer  of  coal  knows  to  be  a  large  item.  It 
reaches  from  ten  to  fifteen  per  cent,  of  the  material 
paid  for.  To  illustrate  the  difficulties  attending  the  use 
of  a  crude  form  of  fuel,  let  us  take  the  most  familiar 
methods,  such  as  are  employed  in  domestic  cooking  and 
heating  (6 J). 

"Ignoring  the  mechanical  imperfections  of  stoves 
and  furnaces,  lest  an  examination  into  them  should 
extend  this  article  unduly,  we  will  examine  the  more 
evident  sources  of  loss: 

"  a.  The  expenditure  of  fuel  in  generating  heat  at 
times  when  it  is  not  utilized.  Every  housekeeper  must 
have  been  struck  with  the  fact  that  a  large  amount  of 
wood  and  coal  is  burned  before  the  range  is  ready  to 
cook,  and  that  a  probably  larger  amount  still  is  used 
after  the  cooking  is  done.  Annoying  as  this  may  be,  it 
is  cheaper  to  keep  the  fire  up  between  meals,  even  in 
Bummer-time,  when  it  is  undesirable,  than  to  let  it  go 
down  and  re-kindle  three  times. 


256  COMBUSTION   OF    COAL. 

"  b.  The  excessive  quantity  employed  while  in  use. 
Often  to  accomplish  some  trifling  result,  like  the  boiling 
of  a  tea-kettle,  the  whole  area  of  fire  space  is  necessa- 
rily kindled,  though  not  more  than  one-tenth  of  it  is 
required.  Twenty  pounds  of  good  anthracite  coal  con- 
tain heat-energy  sufficient  to  raise  two  hundred  and 
seventy  thousand  pounds  of  water  one  degree  in  tem- 
perature, or  seventeen  hundred  and  seventy-six  pounds 
from  sixty  degrees  Fahrenheit  to  the  boiling  point,  two 
hundred  and  twelve  degrees  Fahrenheit,  and  yet  it  is  to 
be  feared  this  power  is  frequently  employed  in  cooking 
a  pot  of  coffee.  If  we  have  expended  for  our  morning 
draught  heat  enough,  if  perfectly  applied,  to  raise  three- 
fourths  ton  of  the  same  liquid  from  atmospheric  tem- 
perature to  boiling  point,  it  may  be  considered  a  some- 
what luxurious  beverage. 

uc.  The  items  of  labor  and  inconvenience  incident 
to  the  use  of  coal  are  too  apparent  to  need  any  enlarge- 
ment. 

"These  are  the  principal  arguments  against  the 
general  use  of  fuel  in  its  natural  condition,  and  they 
appear  formidable  enough  to  justify  the  assertion  that 
not  over  ten  per  cent,  of  the  heating  power  of  such  fuel 
is  utilized. 

"Let  it  be  remembered  that  it  is  in  all  cases  gas  only 
that  we  burn,  and  from  which  we  derive  heat,  so  that 
the  question  is  really  whether  each  family  can  make  a 
limited  quantity  of  the  gas  as  economically  and  success- 
fully in  very  defective  ranges  and  stoves,  as  the  same  or 
a  much  better  article  can  be  manufactured  on  a  large 


GASEOUS    FUEL.  257 


scale  at  some  great  establishment  whence  it  could  he 
distributed  to  consumers.  There  can  be  no  doubt  that 
the  advantage  possessed  by  all  concentrated  industries 
exists  in  this  one  to  at  least  as  great  a  degree  as  in  any 
other  department  of  manufacture.  We  might  as  rea- 
sonably expect  to  grind  our  own  flour,  or  weave  our 
own  fabrics  economically,  as  to  successfully  compete 
with  large  gas-works  properly  constructed  and  skillfully 
managed. 

"  The  advantages  connected  with  the  use  of  a  gas-fuel 
may  be  enumerated  as  follows: 

"  a.  The  cost,  labor  and  inconvenience  of  handling 
a  heavy  material  is  avoided,  the  fuel  being  capable  of 
easy  distribution. 

"6.  It  is  in  a  form  also  free  from  those  material 
impurities  which  involve  a  large  residual  waste,  besides 
impairing  combustion. 

"  c.  It  is  free  also  (if  it  be  a  purely  combustible  gas) 
from  those  ingredients  which,  in  the  present  methods  of 
heating,  involve  even  larger  loss  than  the  cause  last 
mentioned. 

"  d.  It  is  in  precisely  the  condition  to  unite  perfectly 
and  instantaneously  with  the  oxygen  of  the  air,  thus 
securing  a  thorough  combustion. 

"e.     Hence  it  gives  an  immediate  and  uniform  result, 
•     and  its  flame  temperature  is  constant. 

"/.     Til.-   intense  and  steady  heat  of  the  flame  just 
mentioned   saves  both  time  and  money,  by  presenting 
an  even  lire-surface  ready  at  the  moment  of  ignition. 
(18) 


258  COMBUSTION    OF    COAL. 

ug.  It  is  a  fire  capable  of  concentration  upon  the 
precise  point  where  the  result  is  desired,  and  one  that  is 
thoroughly  under  control,  the  turning  of  a  valve  start- 
ing, graduating,  or  stopping  the  combustion  at  will. 

"A.  The  general  cleanliness  of  the  system;  no  dirt 
or  residuals  being  left. 

"i.  The  decided  advantage  from  a  sanitary  stand- 
point of  simply  burning  combustible  gases  in  our  dwell- 
ings, instead  of  attempting  to  make  them  as  well,  by 
means  of  the  imperfect  gas  machines  called  stoves.  In 
the  one  case  the  only  risk  arises  from  the  possibility  of 
a  leak,  readily  detected  by  the  senses,  and  having  simple 
mechanical  remedies;  in  the  other  it  is  a  much  more 
serious  risk,  because  the  defect  is  a  chemical  one,  conse- 
quent upon  imperfect  combustion,  and  the  infusion  of 
poison  into  the  atmosphere  is  likely  to  be  frequent  and 
insidious,  to  say  nothing  of  the  deoxidation  of  the  air 
by  contact  with  red-hot  iron  surfaces.  The  reduction  of 
this  particular  danger  is  about  in  proportion  of  the 
greater  completeness  of  the  combustion  of  the  more 
refined  fuel. 

"  These  facts  appear  to  be  overwhelming  arguments 
in  favor  of  a  gaseous,  as  against  a  gross  form  of  fuel, 
and  lead  to  the  inquiry,  what  gases  are  available  for 
such  purposes? 

"  The  ordinary  coal-gas  made  for  illuminating  pur- 
poses possesses  some  of  the  requisite  qualities.  It  is  a 
combustible  gas  of  great  purity,  of  sufficiently  low 
density  to  render  its  distribution  easy,  and  with  a  high 
flame   temperature;    but,   per   contra,   the    constituents 


GASEOUS    FUEL.  259 


which  impart  the  illuminating  power  are  expensive, 
while  entirely  unnecessary  for  fuel  purposes.  And  yet, 
high-priced  as  it  is,  practical  experience  in  its  use 
proves  that,  in  some  departments  at  least,  it  is  certainly 
cheaper  than  coal,  besides  its  collateral  advantages; 
and  it  is  at  the  present  time  employed,  to  a  limited 
extent,  by  those  who  have  become  familiar  with  the 
tacts.  Exceedingly  interesting  tests  have  been  nrade 
by  the  London  engineers  with  city  gas,  developing 
some  economic  features  in  the  matter  quite  surprising: 
and  at  the  meeting  of  the  American  (4as-Light  Asso- 
ciation, in  1877,  a  paper  was  presented  by  one  of  the 
members  showing  that  careful  experiments  had  so  thor- 
oniddv  demonstrated  its  savins;  even  at  three  dollars 
per  one  thousand  cubic  feet,  that  nine-tenths  of  his  cus- 
tomers were  using  it  in  preference  to  wood  or  coal  for 
kitchen  ami  laundry  purposes. 

"Nevertheless,  coal-gas  can  hardly  be  expected  to 
offer,  for  general  use — domestic  and  industrial — a  sub- 
stitute cheap  enough  to  supplant  coal.  Something  at  a 
still  lower  price  is  needed.  Such  gas  as  is  made  by  the 
Siemens  process,  before  alluded  to,  has  the  advantage  of 
cheapness,  so  far  as  the  mere  relation  of  cost  and  quan- 
tity i-  concerned,  as  it  can  be  produced  at  about  fifteen 
cents  per  one  thousand  feet,  but  its  composition  is  not 
favorable.  It  in  fact  contains  less  than  thirty  per  cent. 
of  combustible  gas.-,  tie'  remainder  being  worse  than 
useless,  besides  rendering  it  too  heavy  for  ready  distri- 
bution at  long  distances. 


260  COMBUSTION   OF    COAL. 

WATER  GAS. 

"A   water-gas — that   is,    a   gas    resulting   from   the 

decomposition  of  steam  by  contact   with   incandescent 

carbon — if  it  can  be  made  cheaply,  possesses  those  very 

qualities  most  desirable  in  a  fuel,  viz,    inflammability 

and  intensity. 

"  Composed  of  hydrogen  and  carbonic   oxide,  it  is 
» 
free  from  the  undesirable  element,  nitrogen;   and  what 

an  advantage  lies  in  that  single  fact,  it  is  hoped  the  fore- 
going explanation  may  have  made  measurably  apparent. 
If  carbonic  oxide  representing  the  maximum  flame 
intensity  (among  practical  gases),  and  hydrogen  with 
but  little  less  of  this  quality,  and  an  even  'greater  use- 
ful value,'  as  Percy  expresses  it,  do  not  furnish  the  very 
highest  order  of  fuel,  then  science  does  not  yet  know 
where  to  seek  it.  Fortunately,  too,  it  is  a  fuel  obtaina- 
ble at  the  lowest  cost,  though  this  is  a  recent  achieve- 
ment. For  more  than  half  a  century  inventors  of  dif- 
ferent nationalities  have  racked  their  brains  for  some 
method  by  which  water-gas  could  be  produced  in  large 
quantities  inexpensively  for  the  industrial  arts,  but 
various  defects  have  invariably  attached  to  the  systems 
proposed  and  rendered  them  unsuccessful. 

"It  requires  the  outlay  of  great  potential  energy  to 
release  the  hydrogen  of  water,  but  the  Lowe  apparatus, 
by  a  system  at  once  original  and  simple,  generates  a 
concentrated  and  sustained  heat  which  does  the  work 
with  a  facility  that  is  astonishing,  yielding  a  volume  of 
fifty  thousand  feet  for  a  ton  of  coal  burned. 


strong's  process  for  generating  fuel  gas.   261 


M.  H.  STRONG'S  PROCESS  FOR  GENERATING  FUEL  GAS. 

"Adopting  the  economic  principle  of  interior  com- 
bustion throughout,  viz,  burning  the  coal  in  a  primary 
chamber,  or  generator,  and  the  products  of  its  partial 
combustion  in  a  secondary  one,  wherein  the  heat  is 
stored  for  subsequent  utilization,  there  are  novel  features 
in  the  Strong  process,  which  give  it  very  definite  advan- 
tages in  the  rapid  and  economic  generation  of  a  com- 
bustible gas  of  remarkable  purity  and  efficiency  for  fuel 
purposes. 

"Reference  to  the  accompanying  diagram,  plate  V, 
will  make  intelligible  the  following  description  of  the 
apparatus  and  its  operation: 

"The  generator  is  charged  with  lump  coal  or  coke, 
entered  at  the  door  in  its  side,  or  from  above  through 
the  opening  left  by  the  removal  of  the  hopper  Z,  which 
is  removable  by  means  of  a  lever  and  tramway.  An 
air-blast  enters  below  the  hydraulic  grate-bars  at  W, 
which  drives  the  tire  and  forces  over  into  the  adjoining 
chambers,  laid  up  with  loose  fire-brick  like  a  Wltitwell 
stove,  the  products  of  partial  combustion  (Siemens  gas), 
which  are  ignited  therein  by  a  second  blast  entering. 
through  a  perforated  tiling  at  .V,  and  burn  downward 
among  the  brick  work,  following  the  direction  of  the 
arrows.  The  third  chamber,  filled,  like  the  second,  with 
refractory  material,  absorbs  a  part,  at  least,  of  the  heat 
of  the  waste  products,  which  escape  at  the  tup  through 
an  open  valve,  shown  in  the  diagram  as  cl08ed. 


262  COMBUSTION   OF    COAL. 

"When  the  coal  has  attained  a  heat  of  say  red  to 
bright  red,  the  brick  of  the  super-heater  (as  the  second- 
ary chambers  are  termed)  show  orange  to  white. 

"The  air-blasts  are  then  shut  off,  the  valve  before 
mentioned  is  closed  as  in  the  cut,  and  steam  is  admitted 
just  below  it  at  Y.  Passing  in  the  reverse  direction  of 
the  arrows,  it  becomes  intensely  heated  by  contact  with 
the  bricks,  from  which  it  emerges  into  the  top  of  the 
generator,  where  it  meets  at  F,  a  shower  of  coal-dust 
sifted  downward  from  the  hopper  Z,  by  means  of  an 
Archimedean  screw  slowly  revolved. 

"  The  steam  has  acquired  such  an  increment  of  heat 
that,  by  contact  with  the  dust-carbon,  a  mutual  decom- 
position instantly  ensues,  and  the  gases  resulting  pass 
downward  through  the  bed  of  coal  and  out  below  the 
grate-bars  into  a  hydraulic  main. 

"Astonishing  as  this  original  method  of  decomposi- 
tion may  appear,  there  is  no  doubt  of  its  occurrence  at 
the  point  V,  as  during  the  earlier  experiments  the  gases 
were  allowed  to  escape  from  the  generator  without 
passing  through  the  incandescent  coal.  There  was 
found,  however,  an  excess  of  carbonic  acid  in  the  pro- 
duct, and  some  unconverted  particles  of  carbon  were 
carried  over.  Both  these  defects  were  remedied  by  the 
passage  of  the  gases  through  the  burning  coal,  the  car- 
bonic acid  changing  to  the  oxide  of  carbon  and  the 
unburnt  dust  being  arrested  and  utilized  as  fuel.  The 
theory  that  the  rapidity  in  evolution  of  the  gas  is  pro- 
portioned to  the  reduced  size  of  the  carbon  particles  is 
fully  confirmed  by  test  made  upon  pulverized  peat,  dur- 


F 


Pf.ATE  V. 


Vertical  Sect.at  A  A 


Vertical  Sect.at  C  C 


M.  H.  STRONG'S  APPARATUS  FOR  GENERATING  FUEL  GAS. 


strong's  process  for  generating  fuel  gas.        263 

ing  which  the  volume  of  gas  for  a  given  period  was 
increased  about  fifty  per  cent,  as  compared  with  the 
coal  slack. 

"The  operations  of  the  apparatus  at  Mount  Vernon, 
in  New  York,  where  experimental  practice  has  extended 
through  the  past  year,  substantiate  the  claim  that  a  pure 
water-gas  can  be  obtained  at  the  expenditure  of  not 
over  2,240  pounds  of  coal  for  each  50,000  cubic  feet. 
Tliis  includes  the  quantity  burned  under  the  boiler, 
which  amounts  to  from  twenty-live  to  thirty  per  cent,  of 
the  whole.  But  it  would  seem  that  this  considerable 
amount  expended  in  the  generation  of  the  steam,  may 
be  saved  by  a  simple  utilization  of  the  heat  of  the  alter- 
cating waste  and  gaseous  products  which,  under  those 
experiments,  escaped  at  from  800°  to  1,200°  Fahr. 

"It  is  confidently  believed  that  if  these  hot  gases 
were  employed  to  heat  the  air-blast  and  the  water,  the 
producl  of  combustible  gas  would  be  increased  to  from 
65,000  to  70,000  cubic  feet  for  each  ton  of  coal. 

"The  most   striking  advantages  of  the  Strong  pro- 
ire, 

"1.  The  extreme  rapidity  with  which  the  gases  are 
generated  in  large  volum 

"2.  The  variety  of  materials  which  may  be  em- 
ployed, ami  their  low  cost. 

"3.     The  remarkable  purity  of  the  product. 

"4.     The  economy  of  the  labor  involved. 

" Regarding  the  firsl  claim,  it  may  he  slated  that  a 
furnace  of  the  dimensions  shown  in  the  diagram  will 
deliver  fully  ten   thousand   cubic  feet  for  each   run  of 


264  COMBUSTION   OF    COAL. 

thirty  minutes.  The  alternate  thirty  minutes  is  used  for 
re-heating,  as  in  the  Lowe  process.  A  pair  of  such 
furnaces  to  secure  continuity  of  operation,  could  be 
relied  on  to  furnish  nearly  live  hundred  thousand  cubic 
feet  per  day,  and  the  labor  requisite  to  run  them  would 
he  hut  two  men  for  each  twelve  hours. 

••  Xot  only  can  anthracite  or  bituminous  coals  he 
used  but  lignites  and  coke  are  available,  and,  what  is 
xcvy  important,  their  culm  or  slack  can  be  employed  in 
(he  proportion  of  three-fourths,  with  very  positive 
advantages.  In  fact,  the  ability  of  this  system  to  utilize 
dust-carbon  has  been  tested  even  to  the  successful  use  of 
peat,  as  already  mentioned. 

'kIt  will  he  seen,  therefore,  that  this  method  does 
not  depend  upon  any  special  forms  of  material,  but,  on 
the  contrary,  employs  many,  some  of  which  are  abund- 
ant and  inexpensive.  In  consequence  of  this  and  the 
advantage  lirst  mentioned,  the  gas  can  be  produced  at 
the  lowest  possible  price. 

"  The  extraordinary  purity  of  the  gas  derived  by 
this  system  is  another  exceedingly  important  fact. 
Analysis  by  Dr.  Gideon  E.  Moore  prove  that  the 
nnpurified  gas  contains  only  12.90  grains  of  sulphur, 
which  is  considerably  less  than  the  legal  limitation  for 
the  purified  gas  furnished  to  London.  But  the  absence 
of  any  large  percentage  of  non-combustible  constituents 
is  far  more  important,  as  will  be  observed  by  the  fol- 
lowing table: 


strong's  process  for  generating  fuel  gas.   265 

Oxygen 0-77 

( 'ail ionic  acid 2.05 

Nitrogen 4.43 

Light  carbonic  hydrogen 4.11 

<  !a rbonic  oxide 35.88 

1 1  ydrogen 52. 16 

"The  relatively  small  proportion  of  1ST  and  CO,  will 
undoubtedly  be  reduced  yet  lower  by  an  apparatus  on  a 
Larger  scale  than  the  one  in  use  at  Mount  Vernon,  as 
the  residual  air  left  in  the  stark  at  the  time  of  shifting 
from  the  blast  to  gas-making  would  be  proportionately 
smaller,  and  this  is  the  principal  source  of  these  non- 
combustibles. 

"It  will  be  apparent  that  this  composition  repre- 
sents the  best  mixture  for  ealorific  purposes  known  to 
science.  It  is  in  striking  contrast  to  that  produced  by 
the  Siemens  furnace,  which,  at  about  the  same  cost, 
contains  about  two-thirds  of  non-combustibles.  This 
serious  drawback  has  been  a  characteristic  of  all  other 
•  ■heap  gases  heretofore,  and  is  a  fatal  objection  in  any 
method  aiming  to  supply  the  general  demands  of  a  fuel 
gas.  Aside  from  the  fact  that  such  a  heavy  dilution 
impairs  the  efficiency  and  value  of  a  gas  to  an  extent 
not  generally  understood,  the  addition  of  such  a  useless 
volume  would  necessitate  an  excessive  size  and  cost  of 
mains  for  its  distribution. 

••  It  becomes  accessary  here  to  explain  a  popular  mis- 
conception which  has  led  many  intelligent  minds  to  an 
entirely  false  conclusion  regarding  the  economic  advan- 
tages of  gaseous  forms  of  fuel  as  compared  with  crude 


266  COMBUSTION   OF   COAL. 

ones.  It  grows  out  of  the  axiom  that  in  the  conversion 
of  the  steam  and  carbon  into  their  resulting  gases  there 
is  an  inevitable  expenditure  of  thermal  force,  so  that 
the  new  form  of  fuel  represents  less  theoretic  units  of 
heat  than  the  old,  and  that,  in  consequence,  there  is  a 
loss  rather  than  a  gain  by  the  exchange. 

"This  is  undeniable,  but  it  is  surprising  that  it 
should  be  so  often  misapplied  in  practical  calculations, 
because  the  comparison  lies  between  the  two  forms  of  fuel, 
not  upon  their  mere  theoretic  calorific  values,  but  upon  the 
useful  effects  obtainable  from  each  in  practice. 

"  The  plain  business  question  which  presents  itself, 
therefore  is,  what  advantage  does  the  Strong  gas  possess 
over  the  coal  from  which  it  was  produced  in  actual 
operations?     Let  us  investigate  this  carefully. 

"The  standard  principle  for  obtaining  the  calorific 
or  beating  power  of  any  fuel  is  to  ascertain  how  many 
weights  of  water  one  weight  of  it  will  raise  one  degree 
of  temperature,  if  burned  under  the  best  possible  con- 
ditions in  air — and  the  number  of  weights  so  deter- 
mined are  called  the  heat-units  of  that  fuel.  These  of 
course  symbolize  its  maximum  calorific  power.  Thus, 
dried  peat  is  said  to  possess  nine  thousand  nine  hundred 
and  fifty-one  units  of  heat;  asphalt,  sixteen  thousand 
six  hundred  and  fifty-five;  good  anthracite,  thirteen 
thousand  per  pound.  That  is,  the  total  heat  of  the 
perfect  combustion  of  one  pound  of  anthracite  would 
raise  thirteen  thousand  pounds  of  water  one  degree 
Fahrenheit.  But  in  estimating  the  practical  heating 
power  of  these  and  other  substances  we  must  remember 


strong's  process  for  generating  fuel  gas.       267 

that  it  is  not  possible  to  obtain  a  result  even  remotely 
approaching  these  figures,  because  instead  of  burning 
them  upon  nicely  adjusted  laboratory  principles,  our 
ordinary  methods  of  combustion  are  grossly  imperfect 
and  extremely  wasteful.  An  explanation  of  the  why 
and  wherefore  of  this  would  be  interesting  did  the 
limits  of  this  article  permit,  but  a  statement  of  the  fact 
with  some  authoritative  comments  thereon  must  suffice. 
Professor  Gruner,  in  a  paper  of  which  the  following 
abstract  was  published  in  the  Engineering  and  Mining 
Journal,  volume  twenty-one,  number  eight,  states  that: 

'"In  the  wind-furnace,  which  is,  from  this  point  of 
view,  the  most  imperfect  apparatus,  there  is  utilized,  in 
the  fusion  of  steel  in  crucibles,  but  1.7  of  the  total  heat 
capacity  of  the  fuel,  or  at  most  three  per  ceut.  of  the 
heal  generated.  In  the  reverberatory,  when  steel  is 
melted  in  crucibles,  the  useful  effect  is  two  per  cent,  of 
the  total  licit.  <>r  three  per  cent,  of  the  heat  generated. 
In  tiir  Siemens  crucible  furnaces,  3  to  3.5  per  cent.;  in 
Siemens  glass  furnaces,  operating  on  a  large  scale,  5.50 
to  6  per  cent.;  in  ordinary  glass  furnaces,  three  per  cent.; 
in  fusion  upon  the  open  hearth  of  a  reverberatory,  of 
glass,  seven  per  cent.;  of  iron,  eight  per  cent. 

"'In  well-arranged  Siemens  and  Ponsard  furnaces, 
up  to  fifteen,  eighteen  and  even  twenty  per  cent,  of  the 
total  heat  is  utilized.  The  calorific  effect  is  much 
greater  when  the  fuel  is  mixed  with  the  material  to  be 
fused.  Large  iron  blast  furnaces  utilize  according  to 
their  working,  seventy  to  eighty  per  cent,  of  the  heat 
generated,  or  thirty-four  to  thirty-six  per  cent,  of  the 


268  COMBUSTION   OF    COAL. 

total  heat  which  the  complete  combustion  of  the  fuel 
would  set  free.' 

"  We  are  thus  furnished  a  basis  of  comparison 
between  the  efficiency  in  actual  practice  of  crude  coal 
and  water-gas,  for  it  is  estimated  that  by  reason  of  its 
instant  mixture  with  the  oxygen  of  the  air,  the  combus- 
tion of  the  gas  is  so  perfect  that  the  heat  generated 
would  be  ninety  per  cent,  of  the  full  theoretic  power  by 
any  rational  system  which  would  use  the  available  heat 
in  the  products  of  combustion. 

"  Therefore,  while  2,240  pounds  of  coal  represent  a 
total  theoretic  value  of  29,120,000  heat-units,  the  value 
really  utilized  by  the  best  modern  blast  furnace,  accord- 
ing to  Professor  Gruner  (thirty-six  per  cent.)  would  be 
9,483,200. 

"The  weight  of  gas  which  the  same  ton  would  pro- 
duce, viz,  two  thousand  and  fifty  pounds,  possesses  a 
total  value  of  18,035,900  heat-units,  of  which  16,232,310 
are  actually  available  in  practice,  showing  an  advantage 
of  the  new  fuel  against  the  old  as  1.71  is  to  1.  This 
advantage,  moreover,  exists  upon  the  basis  of  a  similar 
price  for  the  coal  employed  in  the  two  cases,  while  in 
fact  there  is  a  still  further  gain  in  favor  of  the  gas, 
owing  to  the  fact  that  it  makes  available  a  much  cheaper 
material  (slack)  than  can  be  employed  in  the  direct  fur- 
nace operation  —  a  difference  at  tide- water  of  about 
2.5  to  1. 

"  The  comparison  becomes  still  more  favorable  to 
the  gas  fuel  if  applied  to  ordinary  domestic  uses.  In 
that  department,  it  is  generally  conceded  that  ten  per 


strong's  process  for  generating  fuel  gas.       269 

cent,  of  the  theoretic  heating  power  of  coal  is  the  best 
result  obtained,  so  that  in  these  uses  the  gas  would  have 
an  advantage  of  about  5.57  to  1. 

"  Let  us  now,  for  convenience,  write  down  not  the 
theoretic,  but  the  practical,  available  heat-units  side  by 
side  for  comparison,  as  we  have  ascertained  them 
above. 

ONE  LIS.  COAL.  STRONG  GAS  FROM  1  LB.  COAL. 

(THEORETIC  UNITS  10.000.)  =  |!j"  LB.  GAS. 

, ' ,  (THEORETIC  UNITS  8.798  PER  LB.) 


CRUCIBLE        LARGE       DOMESTIC, 


FURNACES.  BLAST  DO.         USE.  IN    EITHER  USE. 

I',  r  r.-nt  of  heat  'itil- 

ized 3lA  36  10  90 

Units    available   in 

practice 45o  1  680  1,300  7,246 

"This  allows  ten  per  cent,  loss  in  the  combustion  of 
the  gas,  which  is  the  probable  extent  of  this  waste.  In 
some  metallurgical  operations  a  further  allowance  may 
be  necessary  to  cover  an  imperfect  utilization  of  the 
escaping  products,  but  as  this  loss  is  variable  with 
different  methods  we  leave  the  computations  to  the 
reader. 

.  "This,  it  is  insisted,  is  the  proper  method  of  estimat- 
ing the  actual  relative  thermal  values  of  the  two  forms. 
"Beyond  this  firsl  economic  gain  are  collateral  ones, 
affecting  not  only  cost  but  other  equally  important 
questions  of  time  (which  is  a  synonym  for  money)  and 
the  quality  of  the  products.  Take,  for  example,  the 
advantage  of  a  fuel  which  can  be  turned  on  by  a  valve, 
lighted  on  the  instant,  and  extinguished  as  quickly. 
Aside  from  the  tedious  time  necessary  to  the  firing  up 
of  a  metal  furnace,  an   element  of  expense,  how  largely 


270  COMBUSTION    OF   COAL. 

the  labor  incident  to  the  care  of  such  operations  would 
be  reduced. 

"Another  feature  worthy  of  special  comment  is  the 
intensity  of  combustion  of  a  gas  fuel.  The  theoretic 
power  of  the  Strong  gas  is  5483°  Fahr.,  and  the  relation 
of  this  fact  to  rapid  and  economic  operation  is  too  mani- 
fest to  require  argument.  A  furnace  will  often  stand 
indefinitely  at  a  temperature  just  short  of  that  required 
to  accomplish  its  work,  at  an  incalculable  loss  of  time, 
money  and  temper,  and  sometimes  to  the  serious  disad- 
vantage of  the  product.  The  writer  has  seen  a  small 
experimental  reverberatory  for  the  burning  of  this  gas 
ready  to  charge  in  twelve  minutes  from  lighting,  and 
iron  melted  therein  in  eight  minutes  thereafter. 

"Again,  the  constancy  of  this  gas  flame  is  another 
very  marked  advantage,  and  will  enable  the  mechanic, 
once  the  proper  admixture  of  air  is  ascertained,  to  yield 
a  heat  adapted  to  his  special  wants,  to  maintain  a  uni- 
form temperature  and  obtain  a  uniform  result  in  time, 
cost  and  quality. 

"The  whole  subject  is  one  of  peculiar  interest  and 
opens  many  avenues  of  inquiry  and  experiment." 

The  following  is  a  copy  of  a  report  by  Dr.  Gideon  E. 
Moore  on  water  gas  as  made  by  the  apparatus  and  pro- 
cess just  described.  He  visited  the  gas  works  at  Mount 
Vernon,  X.  Y.,  October,  1877,  obtaining  samples  of  the 
gas,  which  were  analyzed  by  him,  with  results  as  given 
below. 

This  report  is  an  interesting  contribution  to  the  lit- 
erature of  gaseous  fuel,  and   though   repeating   much 


FUEL    GAS.  271 


that  has  already  been  said  and  explained  in  the  earlier 
chapters  of  this  book,  it  is  deemed  best  for  the  sake  of 
clearness  and  comparison  to  print  the  report  without 
alteration  or  erasure,  which  is  as  follows: 

••  The  gas  was  made  on  the  day  previous  to  my  visit,  and  I  was 
assured  by  Mr.  Strong  that  no  lime  had  been  used,  nor  other  puri- 
fying agent  except  the  water  in  the  hydraulic  main.  The  gas  was 
allowed  to  pass  freely  from  the  gasholder  through  a  series  of  glass 
tubes  for  two  hours,  to  displace  the  air.  after  which  the  tubes  were 
hermetically  sealed  by  melting  the  ends,  and  the  gas  preserved  in 
this  state  until  required  for  use. 

"  The  specific  gravity  of  the  gas  was  determined  by  direct  weigh- 
ing. Theanalysis  was  made  by  the  methods  laid  down  in  Bunsen  s 
gasometry,  the  more  important  determinations  being  made  in 
duplicate — the  carbonic  oxide,  for  instance,  being  determined 
both  by  eudiometric  analysis  and  by  absorption  with  cuprous 
chloride. 

•■  The  specific  gravity  of  the  dry  gas  was  found  to  be  0.540? 
being  unity,  whence  one  cubic  foot  weighs  0.04116  pound.     The 
composition  by  volume  was  found  to  be  as  follows,  viz: 

0.77 

id -.05 

D 4.43 

ide 

Hydrogen  52.76 

-l.ll 

loo.oo 

bonic  acid  been  completely  reduced  to  carbonic 
oxide,  thegas,  alter  deducting  the  0  77  per  cent,  of  oxygen  and  2.91 
per  cent,  of  the  nitrogen  as  air,  would  have  presented  the  following 
composition,  viz : 

1.55 



Hydrogen 

Marsh  lm~ 4. is 

100.00 

'■  It  is  interesting  to  compare  these  figures  with  tie-  theoretical 
resull  of  the  action  of  steam  on  anthracite  coal. 

"  According  to  Percy,  the  combustible  portion  of  Pennsylvania 
anthracite  consists  of 


272  COMBUSTION   OP    COAL. 


Carbon 94.63 

Hydrogen 2.7:1 

Oxygen 1.28 

Nitrogen 1.36 

100.00 

"  If  we  assume  that  the  2.73  parts  of  hydrogen  are  evolved  in 
combination  with  8.19  parts  of  carbon  in  the  form  of  marsh  gas. 
LOO  parts  of  anthracite,  free  from  ash.  would  require  for  the  complete 
conversion  of  the  residual,  86.44  parts  of  carbon  to  carbonic  oxide 
115.25  — 1.28  =  113.97  parts,  by  weight,  of  oxygen  or  128.22  parts  of 
water.  The  gaseous  products  of  the  transformation  of  one  hundred 
pounds  of  pure  anthracite  would,  therefore,  be, 

Nitrogen 1.3G 

Carbonic  oxide 201. CO 

Hydrogen 14.25 

Marsh  gas 10.92 

22S.22 

or,  reduced  to  per  centages, 

BY    WEIGHT.         BY    VOLUME. 

Nitrogen 0.60  0.32 

Carbonic  oxide 88.38  47.89 

Hydrogen G.24  47.25 

Marsh  gas 4.78  4.54 

100.00  100.00 

"  On  comparing  these  figures  with  the  analysis  of  Strong's  gas, 
it  will  be  seen  that  the  proportion  of  marsh  gas  is  virtually  identi- 
cal in  both  cases,  showing  that  it  must  have  resulted  solely  from  the 
destructive  distillation  of  the  coal,  and  not  by  direct  synthesis.  The 
gas  formed  by  the  action  of  superheated  steam  on  charcoal  possesses, 
according  to  Bunsen,  the  composition, 

Carbonic  acid 14.65 

Carbonic  oxide 29.15 

Hydrogen 56.03 

Marsh  gas 17 

100.00 

"  It  will  be  observed  that  the  amount  of  carbonic  oxide  in 
Strong's  gas  falls  somewhat  short  of  the  theoretical  proportion, 
while  there  is  a  corresponding  excess  of  hydrogen.  This  is  attributa- 
ble partly  to  the  absolution  of  oxygen  in  the  oxidation  of  metallic 
sulphurets  in  the  coal,  partly  to  the  formation  of  carbonic  acid  and 
its  retention  in  the  ash  or  removal  by  solution  in  water,  perhaps 
partly  also  to  the  presence  of  oxidized  products  in  the  small  pr<  - 
portion  of  tar. 


FUEL    GAS.  273 


"  On  the  twenty-eighth  of  December  I  made  a  careful  sulphur 
determination  on  pis  made  in  ray  presence,  and  taken  as  it  flowed 
from  the  scrubbers  to  the  gasholder  ;  no  other  purification  having 
been  employed.  The  gas  was  found  to  contain  12.96  grains  of  sul- 
phur to  the  one  hundred  cubic  feet — an  amount  surprisingly  small 
at  first  sight,  but  less  so  when  we  consider  that  the  two  products  of 
the  action  of  steam  on  highly  heated  sulphurets,  viz.  Sulphureted 
hydrogen  and  sulphurous  acid  immediately  re-act  on  each  other 
with  the  formation  of  free  sulphur  and  water.  It  is,  therefore,  evi- 
dent that  the  sulphureted  hydrogen  in  the  gas  is  simply  the  excess 
over  that  which  is  decomposed  by  the  sulphurous  acid,  and  that  this 
must,  at  the  must,  be  small  in  amount  is  equally  evident  from  the 
fact  that  anthracites  are,  as  a  rule,  much  freer  from  sulphur  than 
bituminous  coal,  and  that  they  are  especially  free  from  the  organic 
sulphur  compounds  which,  by  destructive  distillation,  yield  the  vola. 
tile  sulphur  compounds  so  difficult  of  removal  from  ordinary  coal 
gas.  The  sulphureted  hydrogen  in  the  Strong  gas  is  easily  remov- 
able by  the  simplest  means. 

UALOETFIC   ELEMENTS  OF  THE  STBONG   GAS. 

/.'/"■  ilent — The  theoretical  calorific  equivalent  or  heat- 
ing power  of  combustibles,  is  the  amount  of  heat  evolved  by  the 
combustion  of  the  unit  of  weight  thereof,  expressed  by  the  number 
of  units  of  weight  of  water  which  can  thereby  be  raised  in  tempera- 
ture one  degree  on  the  thermometric  scale. 

"  In  England  and  America  the  unit  of  weight  is  the  avoirdupois 
pound,  the  measure  of  temperature  the  Fahrenheit  thermometer. 
'  >iie  unit  of  heat,  therefore,  is  the  quantity  of  heat  which  will  raise 
the  temperature  of  one  pound  of  water  one  degn n  the  Fahren- 
heit scale,  and  n  units  of  heat  the  amount  which  would  be  required 
to  raise  /,  pounds  of  water  one  degree  Fahrenheit  in  temperature, 
or  one  pound  of  water  ,,  degrees. 

"In  the  case  of  a  compound  combustible,  or,  more  properly.a 
mixture  of  several  combustible  Bubstances,  Like  the  Strong  gas,  the 
theoretical  calorific  equivalent  i>  obtained  by  multiplying  the 
weights  of  the  different  ingredients,  expressed  as  decimals  of  a 
pound,  by  their  Beveral  calorific  equivalents  as  previously  deter- 
mined by  experiment.  The  sum  of  the  numbers  so  obtained 
expresses  the  theoretical  calorific  equivalent  of  the  mixture 
In    the   following  computations    I  have  taken   as  a  basis  the   fig- 

(19) 


274  COMBUSTION    OF   COAL. 


ures  of  Favre  and  Silberman,  whose  experimental  researches  are 
the  most  exact  we  possess. 

"  Applying  these  principles  to  the  analysis  of  the  Strong  gas, 
we  have, 

COMPOSITION  CALORIFIC 

IN    DECIMALS  EQUIVA- 

OF   1    POUND.  LEN1S. 

Oxygen 0.01740  x  0.0  =  0.0 

Carbonic  acid 0.00372  x  0.0  =  0.0 

Nitrogen 0.08798  x  0.0  =  0.0 

Carbonic  oxide 0.70969  x  4325.4  =  3009.7 

Hydrogen 0.07473  x  62031.6  =  4635.1 

Marsh  gas 0.04648  x  23513.4  =  1092.9 

1.00000  8707.7 

Hence  the  theoretical  calorific  equivalent  of  the  Strong  gas  is 
8,798  units  of  heat. 

FLAME  TEMPERATURE. 

"By  the  flame  temperature  is  understood  the  temperature  pre- 
vailing in  the  interior  of  a  burning  mixture  of  gases.  It  may  be 
computed  from  the  calorific  equivalents  when  the  specific  heat  of 
the  gaseous  products  of  combustion  is  already  known.  The  result 
is  very  different,  according  as  the  mixture  burns  under  constant 
pressure,  or  with  constant  volume.  The  first  case  is  the  only  one 
of  which  we  have  here  to  treat. 

"At  62°  Fahrenheit  one  cubic  foot  of  the  Strong  gas  weighs 
0.04116  pound,  and  requires  for  its  perfect  combustion  2.47  cubic 
feet  of  air,  weighing  0.1880  pound.  Proceeding  to  the  computa- 
tion of  the  calorific  equivalent  of  one  pound  of  the  mixture  of  air 
and  gas  in  these  proportions,  we  have, 

COMPOSITION        CALORIFIC 

IN  DECIMALS  EQUIVA- 

OF    1    LB.  LENTS. 

Nitrogen 0.6557  x  0.0  =  u.O 

Carbonic  acid 0.0105  x  0.0  =  0.0 

Oxygen 0.1064  x  0.0  =  0.0 

Carbonic  oxide 0.1174  x  4325.4  =  507.6 

Hydrogen  0.0124  x  62031.6  =  766.5 

Marsh  gas 0.0076  x  23513.4  =  17G.9 

1.0000  1451.0 

whence  the  calorific  equivalent  of  the  mixture  is  1451.0  units. 
The  specific  heat  of  the  products  of  combustion  results  from  the 
following  considerations,  viz : 


FUEL    GAS.  275 


COMPOSITION 
I.V  DECIMALS         SPECIFIC 
OP  1  LB.  HEAT. 

Nitrogen  0.6557      x      0.2-140    =    0.15999 

Carbonic  acid 0.2160       x      0.2164    =<    0.04676 

Water  vapor 0.1283      x      0.4750    =    0.06092 

1.0000  0  26767      - 

whence  the  specific  heat  of  the  products  of  combustion  is  0.26767. 
Dividing  by  this,  the  calorific  equivalent  previously  found,  we  have 

14.51.0  -H  0.26767  =5420.9°  Fahr.. 

i In-  theoretical  elevation  of  temperature  by  combustion  above  the 
initial  temperature  of  the  combustible  mixture.  If  this  initial 
temperature  be  sixty-two  degrees  Fahrenheit,  the  theoretical  tem- 
perature of  the  flame  will  be 

5420.9  +  62  =  5482.9°  Fahr. 

"This  temperature  lies  beyond  the  point  at  which  dissociation 
commences,  and  hence  would  never  be  attained  in  practice,  as, 
however,  Bunsen*  has  shown  that  the  percentage  of  dissociation 
increases  from  the  point  at  which  it  commences,  through  the 
higher  temperatures,  being  for  instance,  in  the  case  of  a  mixture 
in  equivalent  proportions  of  hydrogen  or  carbonic  oxide  and  oxy- 
gen, fifty  per  cent,  at  2,000°C.  =  3,632°F.  and  66|  per  cent,  at 
3.000°C.  =  5,432°F.,  we  may  safely  assume  that  in  the  case  of  differ- 
ent _M-r<  the  temperatures  attained  in  practice  will  be,  within  cer- 
tain limits,  proportional  to  their  respective  theoretical  flame  temper- 
atures,  The  experiments  of  Bunsen  show  that  the  extreme  tem- 
perature  which  may  be  attained  by  the  oxyhydrogen  blast  will  not 
exceed  5,432°  Fahr.  According  to  II.  Valerius-)-  the  theoretical 
flame  temperature  of  ordinary  illuminating  gas  in  pure  oxygen  is 
13,509°  Fain-.,  whereas  in  air  it  is  4,588°  Fahr.,  or  about  900°  Fahr. 
below  that  of  the  Strong  gas. 

"  It  is  hardly  necessary  t<>  add  that  ui-^soeiation  of  the  products 
of  imbustion  only  affects  the  temperature  of  the  flame,  and  has  noth- 
ing to  do  with  tin'  quantity  of  heat  evolved  during  the  combustion. 

ECONOMIC  VALUE  <>F  THE  STKONG  GAS. 

"  In  the  consideration  of  the  economic  value  of  the  Strong  gas 
the  two  applications  which  pre-eminently  demand  our  attention, 
are, 

Poggend  iriTa  Annalen,  CXXXL,  171. 

fLos  Applications  do  la  Chalour. 


276  COMBUSTION    OF    COAL. 


"  1.  Its  value  as  a  substitute  for  other  forms  of  gaseous  or  solid 
fuel,  in  the  arts  and  for  domestic  use. 

"2.  Its  application  for  illuminating  purposes  either,  after 
previously  charging  it  with  illuminating  substances,  as  a  substi- 
tute for  ordinary  illuminating  gas,  or  as  a  diluent  for  very  rich 
coal  gas. 

"Taking  these  subjects  in  the  order  I  have  indicated,  I  first 
pass  to  the  consideration  of 

'■  The  Comparative  Value  of  the  Strong  Gas  as  Fuel — As  lias  already 
been  shown,  the  Strong  gas  possesses  a  heating  power  of  eight 
thousand  seven  hundred  and  ninety-eight  units,  and  a  flame  tem- 
perature of  ">,4s:;D  Fahr.  <  >ne  cubic  foot  of  the  gas.  weighing  at  62° 
Fahr.,  0.0411  pound  requires  for  its  perfect  combustion  2.47  cubic  feet 
of  air,  and  yields  3.027  cubic  feet  of  products  of  combustion,  of 
which  0.610  cubic  feet  is  aqueous  vapor,  and  2  417  cubic  feet  perma- 
nent gases. 

"In  the  combustion  of  gaseous  fuel,  under  normal  conditions, 
and  with  perfect  utilization  of  the  heat  of  the  fire  gases,  the  only 
loss  of  heat  is  from  radiation.  Allowing  ten  per  cent,  as  the  prob- 
able extent  of  this  waste,  we  have,  for  the  effective  heating  power 
of  the  Strong  gas — seven  thousand  nine  hundred  and  eighteen 
units  per  pound,  or  one  hundred  pounds  of  pure  anthracite,  yield- 
ing, as  has  previously  been  shown,  228.22  pounds  of  gas,  would 
develop  in  practice  a  heating  effect  equal  to  228.22  )<  7,917.91  = 
1,807,025  units  of  heat.  The  theoretical  heating  effect  of  coal  being 
thirteen  thousand  units,  the  one  hundred  pounds  of  coal  would, 
if  directly  burned,  develop  one  million  three  hundred  thousand 
units,  of  which,  however,  but  about  fifty  per  cent.,  or  six  hundred 
and  fifty  thousand  units,  would  be  realized  under  ordinary  condi- 
tions in  practice,  hence  the  practical  heating  effect  of  the  gas  stands 
to  that  of  the  coal  from  which  it  was  directly  derived  as  2.78  to  one, 
whereby  it  is,  of  course,  assumed  that  no  loss  of  gas  has  been 
experienced  during  the  manufacture. 

"  In  the  manufacture,  however,  there  is  a  large  consumption  of 
coal  for  heating  the  generator  and  for  the  production  of  steam. 
According  to  the  inventor's  figures,  fifty  jiounds  of  coal  will  pro- 
duce one  thousand  cubic  feet  of  gas,  weighing  41.16  pounds,  and 
possessing  the  theoretical  heating  effect  of  three  hundred  and 
sixty-two  thousand  one  hundred  and  thirteen  units,  of  which  three 
hundred  and  twenty-five  thousand  nine  hundred  and  two  units 
would  be  realized  in  practice.     Fifty  pounds  of  coal  possesses  the 


FUEL    GAS.  277 


theoretical  heating  effect  of  six  hundred  and  fifty  thousand  units, 
of  which  but  three  hundred  and  twenty-five  thousand  would  be 
realized  in  practice  under  ordinary  conditions  and  by  continuous  use, 
as  in  the  generation  of  steam.  Hence,  in  practice,  and  under  equal 
conditions  as  to  radiation  and  continuous  use,  the  gas  will  produce 
the  full  heating  effect  of  the  coal  consumed  in  making  it. 

"The  cost  of  the  gas  being,  according  to  Mr.  Strong's  estimate, 
from  six  to  eight  cents  per  one  thousand  cubic  feet,  and  the  cost 
of  anthracite  being  but  one  dollar  and  a  half  per  ton  for  'pea  and 
•  lust'  coal,  the  cost  of  the  coal  required  would  lie  but  3^  cents. 
whence,  assuming  that  there  can  be  realized  from  such  coal  fully 
fifty  per  cent,  of  the  theoretical  heating  effect,  it  follows  that  for 
such  purposes  as  the  generation  of  steam  with  Mast  air  and  contin- 
uous firing  the  Strong  gas  could  not'compete  with  such  coal. 

"The  case  is,  however,  very  different  in  the  very  numerous 
class  'if  applications,  in  which  the  cheapesl  grade-  of  coal  can  not 
lie  used.  Thus,  with  ordinary  steam  and  manufacturing  coal,  of 
which  the  price  at  New  York  is  at  present  four  dollars  and  a  half 
per  ton.  the  fifty  pounds  of  coal  would  cost  ten  cents,  which,  con- 
trasted  with  the  average  cost  of  the  Strong  gas,  seven  cents,  shows 
the  great  economic  advantages  of  the  latter.  The  advantages  of  gas- 
eous fuel  become  still  more  strongly  apparent  when  we  consider  that 
in  a  very  large  number  of  cases  the  amount  of  heat  which  coal  is 
capable  of  affording  is  but  imperfectly  utilized,  and  that,  in  fact, 
owing  to  the  intermittent  use  of  the  heat,  hut  a  small  proportion 
of  the  theoretically  available  fifty  per  cent,  is  ever  attained.  It  is 
-at'e  to  say  that  for  domestic  me  the  cost  of  the  Strong  gas  would 
lie  at  most  but  fifty  per  cent,  of  the  cost  of  coal  fires,  and  in  sum- 
mer .\en  less. 

" The  only  other  forms  of  gaseous  fuel  with  which  the  Strong 

gas  'an  l>e  compared  ale  coal  gas  and   the  Siemens  gas. 

'While  the  theoretical  heating  effect  of  coal  gas,  viz,  twenty- 
two  thousand  units,  is  about  two  and  a  half  times  that  of  the 
Strong  gas,  the  great  cost  of  the  former  places  it  practically  out  of 
competition. 

" Concerning  the  Siemens  gas  we  have  the  following  data  on 
authority  of  Percy.*  The  average  composition  by  volume  of  the 
gas  at  St.  i robian  is, 

llurgy,  Revised  Edition,  I.,  p.  528.  I  accept  Percy's  statement  of  the  yield 
nf  the  Siemens  gas  with  great  reserve.  Except  on  the  assumption  that  there  has  been 
:in  enormous  loss  during  the  process  of  manufacture,  Ms  estimate  Is  uiucta  too  low. 
As  the  statement,  however,  appears  never  t"  have  been  contradicted,  I  have  employed 
it  in  default  ^f  more  exad  data  for  comparison. 


278  COMBUSTION    OF    COAL. 


Hydrogen 7.50 

Carbonic  oxide 17. no 

Carbonic  add 6.50 

Nitrogen 69.00 

100.00 

and  it  possesses,  according  to  Percy,  the  average  specific  gravity, 
0.78.  One  cubic  foot  at  sixty-two  degrees  Fahrenheit,  would  there- 
fore weigh  0.050  pound.  The  theoretical  heating  effect  deduced 
from  the  foregoing  analysis  is  1101.1  units  of  heat  per  pound. 

"According  to  Percy,  one  ton  of  coal,  free  from  ash,  will  yield 
fifty-thousand  cubic  feet  of  gas.  Assuming  the  coal  to  contain  five 
per  cent,  of  ash,  one  thousand  cubic  feet  of  the  Siemens  gas  would 
require  for  their  production  forty-seven  pounds  of  coal,  and  as  one 
thousand  cubic  feet  weigh  59.38  pounds,  we  have  59.38X1101.1  = 
65,383.3  units  as  the  heating  power,  compared  with  the  340,386 
units  afforded  by  the  nine  hundred  and  forty  cubic  feet  of  the 
Strong  gas  obtained  from  forty-seven  pounds  of  coal.  If,  there- 
fore, we  assume  that  the  Siemens  gas  has  been  made  from  coal  at 
$1.50  per  ton,  and  if  we  leave  out  of  account  the  cost  of  labor, 
repairs  and  all  other  items  of  incidental  expenditure,  we  have, 
as  the  cost  of  the  65,383  units  of  heat  of  the  Siemens  gas  3^  cents,, 
while  one  thousand  cubic  feet  of  the  Strong  gas,  costing  seven 
cents,  will  yield  362,113  units,  or,  in  other  words,  taking  as  the  cost 
of  the  Siemens  gas  the  cost  of  the  coal  required  to  produce  it,  and 
allowing  for  the  Strong  gas  the  inventor's  estimate,  deduced  from 
actual  experience,  of  the  total  cost  of  production,  the  cost  of  a 
given  quantity  of  heat  obtained  from  the  Siemens  gas  is  to  that  of 
the  same  quantity  obtained  from  the  Strong  gas  in  the  proportion 
of  2.5  to  1. 

"  The  theoretical  elevation  of  temperature  produced  by  the 
combustion  of  the  Siemens  gas  is,  as  deduced  from  the  foregoing 
analysis,  2,592  degrees  Fahrenheit,  or,  with  the  air  and  gas  at  the 
initial  temperature  of  62°  Fahr.,  the  temperature  of  the  flame 
would  be  2,654°  Fahr. 

"  One  cubic  foot  of  the  Siemens  gas  requires  0.58  cubic  foot  of 
air  for  its  perfect  combustion,  and  yields  1.46  cubic  feet  of  pro- 
ducts of  combustion,  of  which  1.39  cubic  feet  are  permanent  gases. 

"  For  every  one  thousand  cubic  feet  of  gaseous  products  of 
combustion  from  the  Siemens  gas,  there  are  developed  44,648  units 
of  heat. 


FUEL    GAS.  279 


"  For  every  one  thousand  cubic  feet  of  products  of  com- 
bustion  from  the  Strong  gas,  there  are  developed  119,635  units  of 

heat, 

"  Hence,  for  the  production  of  a  given  quantity  of  heat,  there 
is  formed  with  the  Siemens  gas  2.68  times  the  volume  of  gaseous 
products  that  would  result  from  the  use  of  the  Strong  gas. 

INFLUENCE  OF  THE  .SPECIFIC  HEAT  OF  THE  PRODUCTS  OF  COMBUSTION 
OF  THE  STRONG  GAS. 

11  In  the  foregoing  estimates,  I  have  assumed  that  the  products 
of  combustion  of  the  Strong  gas  have  been  entirely  deprived  of 
their  available  heat,  as  would  be  the  case  in  a  rational  system  of 
practice  wherein  the  waste  heat  of  the  fire  gases  is  used  to  heat 
the  blast,  or,  in  the  case  of  the  generation  of  steam,  the  feed  water 
for  the  boilers. 

"In  the  limited  number  of  cases  where  this  can  not  be  done, 
other  factors  must  be  included  in  the  calculation,  whereby  the 
result  is  to  some  extent  modified,  viz,  the  latent  heat  of  vaporiza- 
tion of  the  water  contained  in  the  products  of  combustion,  and 
the  specific  heat  of  the  permanent  gases  therein. 

"This  correction  becomes  of  special  importance  in  the  consid- 
eration of  the  question  of  a  direct  comparison  between  the  Strong 
gas  and  other  forms  of  fuel,  such  as  coal  and  the  Siemens  gas,  in 
the  combustion  of  which  a  much  smaller  amount  of  aqueous 
vapor  is  formed. 

ig,  for  illustration,  the  simplest  conditions  under 
which  the  problem  could  present  itself,  we  will  take  the  ease 
where  the  products  of  combustion  leave  the  chimney  at  the  tem- 
perature of  two  hundred  and  twelve  degrees  Fahrenheit. 

"In  our  previous  study  of  the  conditions  of  combustion,  1 
have  assumed  that  the  fire  gases  have  been  cooled  down  to  the 
normal  temperature  of  sixty-two  degrees  Fahrenheit,  the  tempera- 
ture at  which  the  air  and  gas  were  presented  for  combustion. 

"One  pound  of  the  Strong  gas  contains, 

i  d 0.0174 

<  larbonic  acid 0.0637 

i  en 0.0880 

i  orbonii  Oxide 0.7097 

Hydrogen 0.0747 

Marsn  gaa 0.0468 

1.0000 

and  requires  for  its  perfect  combustion  5.9052  pounds  air,  yielding 
6.9052  pounds  of  products  of  combustion.  I  >n  multiplying  the 
weights  of  the  several  products  of  combustion  by  the  number  of 


280  COMBUSTION    OF    COAL. 


units  of  heat  required  to  raise  one  pound  thereof  from  62°  to  212° 
Fahr.,  we  obtain  the  following  result,  viz: 

Nitrogen 4.0503  x  (150  x     .2240=   33.G0)  =  15C>.55 

Carbonic  acid 1.4690  x  (150  x    .2104=  32  4<;>  =   47.68 

Water 0.7769  x  (150  x  1.0000  =  150.00)  =  110.53 


6.9052 
Latent  heat  of  the  vaporization  of  the  water 0.7769  x  966=  750.45 


Heat  units  retained   by  tire  gases  at  212    Fahr 1,071.24 

Whence  we  have, 

Calorific  equivalent  of  Strong's  gas 8,798  units 

Latent  heat  of  waste  gases  at  212° 1,071  units 

Utilized 7,727  units 

or,  of  the  total  heating  power  of  the  gas  there  is, 

Wasted 12. is  per  cent. 

Utilized 87.82  per  cent. 


100.00 

"Let  us  see  how  the  Siemens  gas  behaves  under  similar  condi- 
tions.    One  pound  contains 

Nit  logon n.71  W 

<  larbonic  acid 0.1053 

l  'arl ion ie  oxide 0.1752 

Hydrogen 0.0055 

1.0000 

and  requires  for  its  perfect  combustion  0.6380  pound  of  air,  yield- 
ing 1.6380  pounds  of  products  of  combustion.  Proceeding,  as  before, 
we  have, 

Nitrogen 1.2070  x  (150  x  .2240=   33.G0)  =40.59 

Carbonic  acid 3806  x  (150  x  .2104=    32.46)  =  12.37 

Water 040",  x  (150  x  1.000  =  150.00)  =    7.43 


1.0380 
Latent  heat  of  vaporization  of  the  water,  0.0495  x  900= 47. s2 


Heat  units  retained  by  fire-gases  at  212  108.21 

Whence  we  have, 

Calorific  equivalent  of  Siemens  gas 1101.1 

Latent  heat  of  waste  gases  at  212° 108.2 

Utilized 992.9 

or,  of  the  total  heating  power  of  the  gas,  there  is, 

Wasted 9.82  per  cent. 

Utilized 90.18  per  cent. 

100.00 


FUEL    GAS.  281 


"On  the  assumption,  therefore,  that  the  water  formed  by  com- 
bustion is  allowed  to  escape  as  steam,  at  212°  Fahr.,  the  per  cent- 
age  of  loss  of  heating  effect  from  the  latent  heat  of  the  fire  gases 
is  theoretically  slightly  greater  in  the  case  of  the  Strong  gas  than 
in  that  of  the  Siemens  gas.  In  practice,  the  unavoidably  large 
excess  of  air  required  for  the  combustion  of  the  Siemens  gas  would 
cause  the  comparison  to  result  decidedly  in  favor  of  the  Strong  gas. 

"The  application  of  water-gas  in  metallurgy  is  not  new.  We 
are.  on  the  contrary,  informed  by  Percy,*  that  the  gas  produced  by 
the  old  and  costly  method  of  causing  steam  to  re-act  on  coke  in 
cast  iron  retorts  was  seen  by  him  in  operation  for  several  year-,  at 
the  Oldbury  furnaces,  near  Birmingham,  and  that  its  use  had  been 
commenced  in  the  Yorkshire  blast  furnaces. 

"  The  special  advantages  of  the  Strong  gas  for  use  in  metal- 
lurgy are,  apart  from  the  question  of  economy,  the  high  and  easily 
regulated  temperature  it  affords,  and  the  relatively  small  volume  of 
products  of  combustion  compared  with  the  heating  effect.  It  is> 
in  fact,  the  most  concentrated  form  of  gaseous  fuel  hitherto  attain- 
able for  this  application. 

APPLICATION  OF  THE  STRONG  GAS  FOB  ILLUMINATING  PURPOSES. 

'The  Strong  gas  possesses  two  very  valuable  attributes  as 
ds  its  application  for  illuminating  purposes,  either  when  used 
alone  alter  charging  it  with  illuminating  bydrocarbons  or  as  a 
diluent  for  very  rich  coal  gas — the  temperature  of  the  flame, 
namely,  and  the  heating  power.  A<  I  have  already  shown,  the 
Same  temperature  is  some  nine  hundred  degrees  Fahrenheit 
higher  than  that  of  coal  gas,  while  the  quantity  of  heat  evolved 
during  combustion  is  to  that  from  coal  gas  in  the  proportion  of  one 
to  2.5.  This  proportion  would,  of  course,  be  somewhat  changed 
after  the  gas  had  been  charged  with  illuminating  substances,  but 
in  any  event,  with  equal  illuminating  power,  it  will  prove  compara- 
tively free  from  the  tendency  to  beat  the  air  of  the  rooms  in 
wliieli  it  is  burned,  whicb  is  one  of  the  grave  objections  to  ordi- 
nary coal  gas. 

"  The  Buperior  freedom  of  the  Strong  gas  from  Bulphur  is  an 
extremely  valuahle  property  for  illuminating  purposes. 

'•  The  question  naturally  arises  here,  whether  the  use  of  a  gas 

i ni:i_r  ae  shown  by  analysis,  as  much  as  thirty-six  per  cent.  x>f 

carbonic  oxide,  and  which,  under  certain  circumstances,  mighl  pos- 

Bletollurg] ,  1861,  I.,  p.  203. 


282  COMBUSTION    OF    COAL. 


sibly  contain  from  forty  to  forty-five  per  cent.,  would  not  be  attended 
with  danger  to  the  health  of  the  consumer. 

"Leaving  out  of  account  the  fact  that  there  is  even  now  some 
difference  of  opinion  as  to  the  precise  nature  and  extent  of  the 
constitutional  effects  of  air  impregnated  with  a  small  proportion  of 
carbonic  oxide,  it  would  be  obviously  absurd  to  base  any  estimate 
on  the  poisonous  nature  of  the  pure  gas,  or  even  on  the  proportion 
contained  in  the  Strong  gas.  The  question  can  only  be  decided  by 
comparison  with  our  previous  experience  with  other  illuminating 
gases  of  known  composition. 

"  Were  carbonic  oxide  the  only  poisonous  ingredient  in  coal 
gas  there  might  appear  to  be  some  foundation  for  the  reasoning  of 
the  opponents  of  such  gases  as  the  Lowe  gas,  that  if  coal  gas,  which 
rnay  contain  as  much  as  fifteen  per  cent,  of  carbonic  oxide,  be  poison- 
ous, a  gas  which  may  contain  thirty  per  cent,  must  necessarily  be 
twice  as  much  so.  Unfortunately  for  this  chain  of  reasoning,  car- 
bonic oxide  is  not  the  only,  or  even  the  most,  poisonous  ingredient 
in  coal  gas.  The  heavy  hydrocarbons,  especially  the  vaporized 
tarry  substances,  may  produce,  when  mixed  even  in  slight  propor- 
tion with  the  air,  vertigo,  insensibility  and  even  death.  According 
to  Jacobs*  the  contents  of  as  much  as  three  (3)  per  cent,  of  coal 
gas  in  the  air  of  a  room  is  fatal  to  human  life.  If  we  accept  the 
still  smaller  proportion  of  one  per  cent,  of  carbonic  oxide  as  the 
minimum  quantity  required  to  produce  an  injurious  effect,  then 
fully  three  per  cent,  of  such  a  gas  as  the  Lowe  gas  would  have  to  be 
present,  whence  it  follows  that  the  amount  of  such  gas  necessary  to 
produce  an  injurious  effect  would  practically  amount  to  a  fatal  dose 
of  ordinary  coal  gas. 

"  The  absurdity  of  claiming  that  a  gas  containing  as  much  as 
twenty-five  to  thirty  per  cent,  of  carbonic  oxide  is  necessarily  dan- 
gerous, will  best  be  apparent  from  the  consideration  of  the  amounts 
contained  in  wood  gas — a  material  largely  used  wherever  the  relative 
cost  of  wood  and  coal  renders  it  economically  advantageous.  I  give 
below  the  proportions  of  carbonic  oxide  found  in  different  kinds  of 
wood  gas: 

KIND   OF  GAS.  CARBONIC  OXIDE.  ANALYST. 

Not  specified 61.79  Pettenkofer. 

Crude 37.62  Pettenkofer. 

Crude 28.21  Pettenkofer. 

From  Beech  Wood 41.94  Reissig. 

From  Birch  Wood 35.99  Reissig. 

From  Pine  Wood 38.25  Reissig. 

From  Turf 20.33  Reissig. 

*  Quoted  in  Stohmann-Muspratt's  Chemie,  3d  Ed.,  IV.,  623. 


FUEL    GAS.  283 


"  In  the  year  1862,  the  following  European  towns  were  lighted 
with  wood  gas,  viz,  Coburg,  Wurzburg,  Darmstadt,  Giessen,  Zurich, 
St.  Gall,  Sehaffhausen,  Aarau,  Lucerne,  Regensburg,  Landshut, 
Erlangen,  Ulm,  Kempton,  Linz,  Chur,  Freiburg  (in  Switzerland)', 
and  many  others.  I  have  been  unable  to  find  that  the  question  of 
possible  danger  from  the  presence  of  carbonic  oxide  in  wood  gas  has 
ever  been  raised. 

"  Th  to  water  gas  in  general  on  account  of  its  contents 

in  carbonic  oxide  are  based  on  an  entire  misconception  of  the 
meaning  of  the  reports  of  the  eminent  scientific  men  who  were 
called  to  pronounce  upon  the  question  of  its  safety  in  France. 
The  French  report  was  unfavorable  for  the  following  reasons: 

"The  gas  was  not  saturated  with  illuminating  hydrocarbons 
and  was  consequently  inodorous;  it  was  not  of  itself  luminous,  but 
was  employed  to  heat  to  intense  whiteness  small  cages  of  platinum, 
which  were  suspended  in  the  flame  and  furnished  the  luminous 
body.  Being  inodorous,  the  escape  of  the  gas  could  not  have  been 
detected,  hence  the  dangers  arising  from  accidental  leakage  were 
excessive.  It'  the  Strong  gas  be  made  luminous,  it  must,  like  the 
Lowe  gas,  n  ceive  a  strong  and  characteristic  odor.  Herein  lies, 
also,  the  only  element  of  safety  in  the  use  of  ordinary  coal  gas, 
jjjjjjjjj  of  which  can  be  detected  in  air  by  its  odor.  Coal  gas,  if  ino- 
dorous, would  in  all  respects  be  as  dangerous  for  domestic  use  as 
pure  carbonic  oxide  gas. 

' '  i    I  hesitation  in  stating  as  my  opinion,  that  'water- 

gas,'  either  the  Low.-  gas  or  the  Strong  gas,  when  properly  'car- 
bureted,'  is  in  all  respects  as  safe  for  household  use  as  ordinary 
coal  gas. 

■■  '    i  better  conclude  my  report   than   by  stating  my 

entire  concurrence  in  the  opinion  of  the  greatest  living  authority 
in  chemical  technology,  Rudolph  Wagner,*  who,  after  alluding  to 
the  lack  -  of  the  previous  attempts  to  introduce  water- 

gas,  owing  to  imperfect  apparatus,  Bays:  'Nevertheless,  water-gas 
:-till  appears  to  us  to  be  the  illuminating  gas  of  the  future.' 

"  Respectfully  submitted  by  your  obedient  servant, 

"  <  rlDEOH    E.   Mookk,  Ph.  D. 
"J ERSE?  <  'i  iv.  Jaki  \ky  22,  1  VT^ 
•  To  •-     .1   ■  I  Light  Company,  New  York." 


Jahresbericbl  der  Chemischen  Technologic,  1874,  p.  901. 


CHAPTER    XVII. 

UTILIZING  WASTE  GASES  FROM  THE  FURNACE. 

Waste  Products — Magnitude  of  the  Loss — Siemens'  Regenerative 
Gas-Furnace. 

The  waste  products  of  furnaces  may  be  divided  into 
two  classes: 

1.  The  escape  of  gases  in  which  combustion  has 
been  incomplete.  This  is  confined  almost  exclusively  to 
carbonic  oxide,  a  combustible  gas,  formed  in  the  furnace 
by  a  too  little  supply  of  oxygen  at  the  time,  or  during 
the  process  of  combustion. 

2.  The  escape  of  heated  products  which  may  in 
themselves  be  incombustible,  but  having  passed  their 
point  of  application,  are  rendered  unavailable  to  the  pur- 
poses for  which  they  were  generated,  and  are  thus  a 
source  of  loss. 

In  blast  furnaces,  waste  gases  are  made  to  serve  a 
useful  purpose  in  generating  steam,  heating  the  blast, 
etc.;  in  puddling  furnaces,  by  heating  a  steam  boiler, 
which  is  usually  placed  directly  over  the  furnace;  and 
in  many  other  ways  these  waste  gases  are  partially 
utilized.  To  show  the  necessity  for  utilization,  and  the 
magnitude  of  this  loss  in  case  of  neglecting  to  do  so, 
was  clearly  stated  in  a  lecture  given  by  Dr.  Siemens,  on 
Fuel  (1873),  in  which  he  says:  "Taking  the  specific 
heat  of  iron  at  .114,  and  the  welding  heat  at  2,900° 
Fahr.,  it  would   require  .114  X  2,900  =  831  heat  units 


SIEMENS'    REGENERATIVE    GAS-FURNACE.  285 

to  heat  one  pound  of  iron.  A  pound  of  pure  carbon 
developes  14,500  heat  units,  a  pound  of  common  coal,  say 
12,000 ;  and,  therefore,  one  ton  of  coal  should  bring 
thirty-six  tons  of  iron  up  to  the  welding  point.  In  an 
ordinary  re-heating  furnace,  a  ton  of  coal  heats  only 
1|  ton  of  iron,  and,  therefore,  produces  only  -,1-  part  of 
the  maximum  theoretical  effect. 

"Ill  melting  one  ton  of  steel  in  pots  two  and  a-half 
tons  of  coke  are  consumed,  and  taking  the  melting 
point  of  steel  at  thirty-six  hundred  degrees  Fahren- 
heit, the  specific  heat  at  .119,  it  takes  .119  X  3,000 
=  428  heat  units  to  melt  a  pound  of  steel,  and  tak- 
ing the  heat-producing  power  of  common  coke  also 
at  twelve  thousand  units,  one  ton  of  coke  ought  to  be 
able  to  melt  twenty-eight  tons  of  steel.  The  Sheffield 
pot  steel  melting  furnace,  therefore,  only  utilizes  -^- part 
of  the  theoretical  heat  developed  in  the  combustion." 

These  tacts  led  Dr.  Siemens  as  early  as  1846  to  con- 
sider the  practicability  of  storing  this  waste  heat  and 
utilizing  it  again  and  again.  In  this  he  was  successful, 
and  bia  regenerative  furnace  marks  an  era  in  the  util- 
ization of  waste  gases. 

Siemens''  Regenerative  Gas-furnace — The  construction 
of  this  furnace  is  shown  in  plate  IV;  a  description 
and  its  mode  of  operation  are  clearly  set  forth  in  the 
specification  of  his  American  patent  given  below: 

••  In  the  accompanying  plate  of  drawings,  in  which 
corresponding  parts  arc  designated  by  similar  letters, 
figure  1    is   a  partial  longitudinal   vertical  section  of  the 


286  COMBUSTION   OF    COAL. 

furnace.  Figure  2  is  a  horizontal  longitudinal  section, 
showing  the  relative  position  of  the  air  and  gas  flues. 
Figure  3  is  a  transverse  vertical  section  of  the  furnace 
through  the  cave  A.  Figure  4  is  a  transverse  vertical 
section  through  the  air  flues.  Figure  5  is  a  longitudinal 
elevation. 

"  The  regenerative  gas-furnace,  as  shown  in  the 
drawings,  is  built  of  fire-brick  or  other  suitable 
refractory  material,  and  consists  of  the  four  regen- 
erators with  the  flues  and  valves,  and  the  heating- 
chamber,  where  the  metallurgical  operations  are  car- 
ried on. 

"  The  four  regenerators  are  arranged  in  pairs,  and 
vary  in  size,  the  smaller  being  used  for  the  passage  of 
gas,  and  the  larger  for  that  of  air,  their  proportions 
being  in  the  ratio  of  two  to  three.  Approximately, 
these  ratios  correspond  to  the  quantities  of  gas  and  air 
required  to  insure  complete  combustion  in  the  heating- 
chamber.  The  walls  of  the  regenerators  are 
built  of  fire-brick  or  other  suitable  refractory  mate- 
rial, closely  laid  and  white-washed,  or  other- 
wise made  gas-tight,  so  that  no  leakage  may 
take  place  from  one  chamber  to  another.  These 
chambers  are  filled  with  refractory  material,  by  prefer- 
ence fire-brick,  stacked  loosely  together,  and  each  regen- 
erative chamber  has  its  own  separate  flue  at  the  base, 
communicating  with  the  valves  by  which  the  gas  and 
air  enter,  or  the  products  of  eombustion  pass  out,  while 
from  the  top  or  side  of  each  regenerative  chamber  a 
series  of  flues  pass  upward  and  communicate  with  the 


SIEMENS'    REGENERATIVE    GAS-FURNACE.  287 

heating  chamber;  and  I  prefer  to  cause  the  air  to  enter 
the  heating  chamber  above  the  gas,  as  by  its  superior 
specific  gravity  at  equal  temperatures  it  tends  to  sink 
through  the  eras,  and  thus  an  intimate  mixture  and  more 
perfect  combustion  is  obtained.  The  entering  or  issuing 
gaseous  currents  pass  through  valves,  which  are  shown 
in  x  in  figure  3. 

"The  heating  chamber  where  the  metallurgical  pro- 
cesses are  carried  on,  has  its  roofs  and  sides  constructed 
of  highly  refractory  materials,  such  as  best  silica  or 
Dynas  bricks.     The  bed  is  usually  made  of  sand. 

••  Below  the  center  of  the  furnace  is  an  open  cave,  A, 
through  which  air  freely  circulates,  and  rises  through 
openings  into  the  air-space  below  the  melting  chamber 
and  behind  the  bridges,  whereby  a  perfect  cooling  of 
the  sides  of  the  melting  chamber  is  effected.  This  cave 
serves,  moreover,  as  a  receptacle  for  any  metal  which 
may  break  through  the  sides  or  bottom  of  the  melting 
chamber,  whence  it  can  be  removed  at  leisure,  without, 
meanwhile,  encumbering  the  ventilating  spaces  around 
the  melting  chamber. 

"On  first  lighting  the  furnace,  the  gas  passes 
through  the  proper  valves  and  flues  into  the  bottom  of 
regenerator  chamber  c,  while  the  air  enters  through 
corresponding  valves  and  flues  into  the  regenerator 
chamber  h\  which  should  be  about  one-half  Larger  than 
the  gas  regenerator  chamber  c.  The  currents  of  gas 
and  air,  both  quite  cold,  rise  separately  through  the 
regenerators  c  and  F,  and  pass  up  through  the  series  of 
flues  G  G  G  G  G  and  F  F  F  F  F,  respectively,  into 


288  COMBUSTION   OF    COAL. 

the  furnace  above,  where  they  meet  and  are  lighted, 
burning  and  producing  a  moderate  heat.  Each  air- 
port rises  from  its  regenerator  behind  the  corresponding 
gas-port,  and  is  projected  into  the  furnace  over  such 
gas-port,  it  being  important  that  the  air-port  should 
overlap  the  gas-port  on  both  sides.  Great  solidity  of 
brick  work  and  perfect  combustion  is  thereby  attained. 
"The  products  of  combustion  pass  away  through  a 
similar  set  of  flues  at  the  other  end  of  the  furnace,  into 
the  regenerator  chambers  c'  E',  which  are  not  shown  in 
the  drawings,  but  are  symmetrical,  both  in  construc- 
tion and  arrangement,  with  the  chambers  c  E,  already 
described.  The  products  pass  from  thence,  through 
properly-constructed  flues  and  valves,  to  the  chimney- 
flue.  The  waste  heat  is  thus  deposited  in  the  upper 
courses  of  open  fire-brick  work,  filling  the  chambers 
c'  E,  and  heats  them  up,  while  the  lower  portion  and 
the  chimney-flues  are  quite  cool ;  then,  after  a  suitable 
interval,  the  reversing  flaps — through  which  the  air  and 
gas  are  admitted  or  withdrawn  from  the  furnace — are 
reversed,  and  the  air  and  gas  enter  through  those  regen- 
erator chambers  E'  c',  which  have  been  just  heated  by 
the  waste  products  of  combustion,  and  in  passing  up 
through  the  checker-work  they  become  heated,  and 
then,  on  meeting  and  entering  into  combustion  in  the 
furnace  _D,  they  produce  a  very  high  temperature,  the 
waste  heat  from  such  higher  temperature  of  combustion 
heating  up  the  previously  cold  regenerators  c  E,  to  a 
corresponding  higher  heat.  Thus  an  accumulation  of 
heat  and  an  accession  of  temperature  is  obtained  step 


C.W.  SIEMENS. 

REGENERATIVE    GAS   FURNACES. 


FlGli. 


FIG.  i. 


*\ 


SIEMENS'    REGENERATIVE    GAS-FUNNACE.  289 

by  step,  so  to  speak,  until  the  furnace  is  as  hot  as 
required.  The  heat  is,  at  the  same  time,  so  thoroughly 
abstracted  from  the  products  of  combustion  by  the 
regenerators,  that  the  chimney-flue  remains  compara- 
tively cool. 

"  The  command  of  the  temperature  of  the  furnace,, 
and  of  the  quality  of  the  flame,  is  rendered  complete  by 
means  of  gas  and  air-regulating  valves,  and  by  the  chim- 
ney damper." 


(20) 


CHAPTER  XVIII. 

A.  PONSARD'S  PEOCESS  AND  APPARATUS  FOR  GENERAT- 
ING GASEOUS  FUEL. 

The  following  is  a  copy  of  the  specifications  of 
Anguste  Ponsarcl,  Paris,  France,  describing  in  detail  his 
process  and  apparatus  for  generating  gaseous  fuel : 

"It  is  the  object  of  my  invention  to  increase  the 
production  of  carbonic  oxide  from  a  given  quantity  of 
fuel ;  to  produce  this  gas  at  the  highest  possible  temper- 
ature, so  as  (without  passing  it  through  any  cuperator  or 
regenerator)  to  introduce  it  at  the  highest  possible  tem- 
perature to  the  furnace  in  which  it  is  to  be  consumed; 
to  support  the  combustion  of  this  gas  by  the  introduc- 
tion to  the  furnace  of  air  previously  heated  by  the 
waste  products  of  combustion,  and  to  simplify  the 
apparatus  required  for  the  production  and  consumption 
of  gaseous  fuel,  while  attaining  a  higher  heat  than  has 
been  heretofore  obtained  therefrom. 

"Previous  to  my  invention,  when  the  highest  heats 
from  gaseous  fuel  have  been  required  it  has  been  neces- 
sary that  the  temperature  of  the  gas  should  be  raised 
before  its  introduction  to  the  furnace  for  combustion, 
not  only  because  it  could  not  be  produced  at  a  suffi- 
ciently high  temperature,  but  because  much  of  its  orig- 
inal heat  had  been  lost  in  its  passage  from  the  producer 
to  the  furnace,  in  most  instances  widely  separated.  In 
that  system  the  expense  of  the  apparatus  is  meieased, 


poxsard's  process  and  apparatus.  291 

not  only  b}T  the  cost  of  the  separate  structures,  but  by 
the  means  required  to  connect  them;  and  as  the  more 
volatile  particles  of  the  gas  are  deposited  in  passing 
from  the  producer  toward  the  furnace,  and  in  restoring 
the  heat  by  the  recuperator  the  gas  deposits  another 
portion  upon  the  recuperator,  this  operation  is  attended 
with  a  constant  waste  of  fuel. 

"  My  invention  consists,  first,  in  supporting  the  com- 
bustion of  the  gas-producing  fuel  by  supplying  it  with 
a  continuous  current  of  highly-heated  air,  and  so  regu- 
lating this  supply  as  to  control  the  activity  of  the  com- 
bustion; second,  in  defining  the  traverse  of  this  air,  and 
the  gas  produced  thereby,  so  that  the  gas  shall  pass  off 
at  the  highest  temperature;  and,  third,  in  effecting  an 
intense  combustion  by  the  introduction  to  this  gas,  as  it 
passes  to  the  furnace,  of  air  previously  heated  by  the 
waste  products  of  combustion. 

"At  the  ordinary  temperature  of  the  atmosphere,  the 
.air  and  the  fuel  for  the  production  of  carbonic-oxide 
gas  will  not  combine  with  sufficient  rapidity  to  produce 
sensible  heat.  The  rapidity  of  their  combination  and 
the  intensity  of  the  resultant  heat  arc  probably  in  pro- 
portion to  the  temperature  of  the  two,  respectively. 
previously  to  their  combination. 

"In  gas-producers,  as  heretofore  ((instructed,  the  gas- 
producing  fuel  performs  two  functions — first,  to  heat 
the  air  and  the  fuel  to  a  sufficient  temperature  to  con- 
tinue an  active  combustion,  producing  carbonic-acid  gas, 
and,  second,  to  heat  the  remaining  find  to  such  a  degree 
that  a  slower  combustion  withoul   flame  will  take  place. 


292  COMBUSTION    OF    COAL. 

in  which  the  carbonic  acid  should  take  up  another  charge 
of  carbon  and  become  carbonic  oxide;  but  in  all  such 
producers  a  portion  of  the  carbonic  acid  will  pass 
through  without  taking  up  another  charge  of  carbon. 

"Now,  if  the  air  which  is  to  support  the  primary 
combustion  should  be  so  heated  that  none  of  the  heat 
from  the  fuel  would  be  required  for  the  primary  condi- 
tions, the  carbonic  acid  would  be  produced  at  a  much 
higher  temperature,  and  its  liability  to  pass  through  the 
remaining  fuel  without  taking  up  another  charge  of 
carbon  would  be  diminished,  so  that  the  product  of 
carbonic  oxide  from  a  given  quantity  of  fuel  would  be 
greater  than  has  heretofore  been  obtained.  Moreover, 
the  air  coming  to  the  fuel  heated,  instead  of  to  he 
heated,  not  only  promotes  the  combustion  of  the  fuel 
and  the  production  of  carbonic  oxide,  but  it  also  inten- 
sifies the  temperature  of  this  gas  by  the  direct  contribu- 
tion of  heat  instead  of  abstracting  it,  as  heretofore. 

"It  must  be  borne  in  mind  that  the  consumption  of 
fuel  at  any  temperature,  however  high,  will  be  propor- 
tioned to  the  quantity  of  air  admitted  to  combine  with 
it,  so  that,  while  the  quantity  of  air  admitted  is  kept 
within  the  limits  which  must  be  observed  to  prevent  a 
too  active  combustion,  the  result  obtained  will  be  an 
increased  quantity  of  carbonic  oxide  at  a  higher  tem- 
perature than  has  heretofore  been  possible. 

"  In  the  accompanying  drawings  I  have  shown  an 
improved  apparatus,  in  which  the  operation  of  my 
invention  is  exemplified. 


PONSARD'S   PROCESS    AND    4.PPARAT 

"Figure  1  represents  a  vortical  longitudinal  section 
of  my  improved  apparatus  applied  to  a  heating-furnace, 
line  of  section  A  B,  figure  2.  Figure  2  is  a  horizontal 
section  thereof,  following  the  line  C  D,  figure  1.  Fig- 
ure 3  is  a  vertical  transverse  section  on  the  line  a  b,  fig- 
ure 1.  Figure  4  is  a  vertical  transverse  section  on  the 
line  1  J,  figure  1.  Figure  5  is  a  vertical  transverse  section 
on  the  line  c  d,  figure  1.  Figure  6  represents  in  detail, 
and  upon  an  enlarged  scale,  the  hollow  bricks  which  I 
use,  and  the  manner  in  which  they  are  put  together  in 
the  recuperator.  The  principal  feature  in  their  con- 
struction is  the  recessed  ends  s,  which,  when  in  position, 
as  at  sf  s',  form  chambers  in  which  fire-clay  can  be 
packed,  so  as  to  form  a  key  to  hold  the  structure 
together,  as  well  as  an  interruption  to  the  passage  of 
gas  and  air  at  the  joint.  This  general  arrangement  of 
the  recuperator  is  the  same  as  described  in  l"1' 
ent  of  the  United  States  Xo.  130,313,  granted  to  me 
August  6,  1872. 

"The  gas-producer  consists  of  a  rectangular  cham- 
ber, a,  the  lower  part,  b,  of  which  is  greatly  contracted, 
in  order  that  the  residuum  of  the  fuel  (cinders  and  slag) 
in  the  contracted  space,  b,  may  be  easily  removed  with 
stoking-irons. 

"The  fuel  is  charged  through  the  hopper  and  clap- 
valve  c,  and  the  arch  d  serves  to  limit  its  height  in 
chamber  a.  The  fuel  is  supported  by  the  hearth  p, 
upon  which  the  cinders  and  slag  will  accumulate,  and 
from  which  they  may  he  removed,  as  hereinafter 
described.    The  hot  air  is  brough.1  from  the  recuperator 


294  COMBUSTION    OF    COAL. 

i  to  the  front  of  the  producer  through  the  conduit  e, 
and  reaches  the  fuel  through  the  opening  /,  which 
takes  up  nearly  the  whole  width  of  the  chamber  a. 

"The  ash-pit g  can  be  closed  by  means  of  vertically- 
sliding  doors  of  sheet-iron,  h,  which  are  raised  by  means 
of  counter-weights;  or  it  may  remain  open  if  the  press- 
ure of  the  hot  air  entering  the  producer  is  not  great 
enough  to  force  back  the  gas  through  this  part  of  the 
apparatus.  To  prevent  the  loss  of  gas  which  might 
result  from  its  driving  back  under  pressure,  the  sliding 
doors  may,  after  each  clearing  of  the  pit,  be  luted  with 
ashes,  earth  or  sand. 

"In  the  front  wall  of  the  contracted  portion  b  of  the 
producer,,  above  the  arch  of  the  ash-pit,  openings  j  are 
provided,  through  which  stoking-irons  may  be  intro- 
duced, to  lift  and  stir  the  fuel;  and  to  remove  the  ashes 
and  slag  to  the  lower  part  of  the  apparatus  through  the 
openings  j,  bars  may  be  inserted  to  sustain  the  fuel 
above  the  hearth,  and  within  the  producer,  while  the 
ashes,  cinders  or  slag  are  being  removed  from  the 
hearth  p  beneath  the  bars.  In  the  side  walls  of  the 
producer  are  also  provided  openings  k,  which,  together 
with  the  sight-holes  I,  arranged  in  the  arch,  allow  the 
introduction  of  stoking-irons  to  compact  the  fuel,  and 
to  break  up  any  arches  that  may  be  formed  by  the 
agglomeration  of  coal,  especially  if  a  rich  kind  of  coal 
is  used.  The  recuperator  i  is  divided  into  two  parts, 
one  of  which  serves  to  heat  the  air  required  to  support 
combustion  in  the  producer,  and  the  other  to  heat  the 
air  for  the  combustion  of- the  gas  as  it  enters  the  fur- 


ponsard's  process  and  apparatus.  295 

nace  by  moans  of  the  passage  m.  This  division  of  the 
recuperator  into  two  distinct  parts  may  be  made  com- 
plete or  partial  only;  in  other  words,  they  may  be 
entirely  separated  by  a  solid  wall,  or  the  transverse  air- 
passages  only  may  be  filled  up  (divided)  by  solid  bricks, 
leaving  the  passages  for  products  of  combustion  in  com- 
munication. This  latter  disposition  is  represented  in 
the  drawing. 

••Whatever  arrangement  may  be  adopted,  independ- 
ent valves  must  be  placed  before  each  group  of  ori- 
fices for  the  admission  of  air  into  the  divided  recup- 
erator, to  regulate  the  quantity  of  air  admitted  to  the 
producer,  as  well  as  to  the  furnace.  In  the  drawings, 
the  position  of  these  valves  is  represented  at  ??,  figure  1, 
in  the  rear  of  the  recuperator,  and  they  are  operated  by 
screwed  rods  n'  and  hand-wheels  o. 

••  With  a  view  to  obtain  the  maximum  advantages  of 
my  improved  system  hereinbefore  d  I ,:'  1.  T  contem- 
plate varying,  under  varying  circumstances,  the  con- 
struction of  the  producer,  with  the  view,  in  all  cases,  to 
admil  the  air  above  the  hearth,  to  define  its  traverse 
through  the  fuel,  and  to  carry  off  the  carbonic  oxide 
from  that  section  of  the  producer  where  this  gas  is  the 
hottest. 

"In  the  disposition  represented  in  figures  7  and  8,  the 
gas-producer  consists  of  a  vertical  chamber,  a  (which  is 
charged  with  fuel  by  means  of  two  ordinary  valve-boxes, 
//),  tin'  lower  portion  of  which  presents  openings  upon 
opposite  side-,  by  means  of  which  the  cinder  ami  ashes 
may  he  removed.     To  tin-  end  the  lower  portion  of  the 


296  COMBUSTION    OF   COAL. 

space  a  terminates  in  two  inclined  planes,  c,  extending 
down  to  a  certain  distance  above  the  ground,  in  such 
manner  that  raking-bars  may  be  easily  inserted  into  the 
openings  thus  provided,  to  remove  and  loosen  the  ashes 
and  cinders  accumulating  in  this  portion  of  the  pro- 
ducer. In  this  disposition  the  conduit  b  for  the  out- 
going gas  is  placed  lower  than  shown  in  the  drawings, 
figures  1  to  5,  and  is  elevated  above  the  plane  of  the 
conduit  c,  for  the  admission  of  air,  so  that  the  air  will 
traverse  the  fuel  in  a  slightly-ascending  plane. 

"Figures  9  and  10  represent  a  gas-producer,  a,  which 
from  the  top  to  its  base  presents  the  form  of  a  frustum 
of  a  pyramid.  This  is  varied  in  width  according  to  the 
nature  of  the  combustible  employed.  In  this  disposition 
the  conduit  b  of  the  out-going  gas  is  placed  at  the  same 
height  with,  or  even  a  little  lower  than,  the  conduit  c, 
supplying  the  hot  air,  and  the  two  orifices  of  these  con- 
duits are  fitted  with  a  grating,  d,  forming  a  part  of  the 
inclosure  of  the  space  a.  This  grating  is  constructed  of 
refractory  pieces  (as  bricks),  the  shape  of  which  may 
vary,  while  they  are  so  disposed  as  to  leave  sufficient 
sectional  area  for  the  air  and  gas.  These  bricks  are 
simply  built  up  without  the  interposition  of  any  mortar, 
so  that  they  may  be  easily  replaced  (when  deteriorated) 
through  the  openings  e,  provided  in  the  two  parallel  long 
sides  of  the  producer.  The  lower  part  of  the  apparatus 
is  closed  by  loose  walls  /,  which  are  withdrawn  to 
remove  the  ashes  produced  by  combustion,  the  coal 
remaining  supported  during  this  time  by  the  grate  g, 


ponsard's  process  and  apparatus.  297 

the  removal  of  a  few  bars  of  which  will  allow  the  cin- 
ders accumulated  iu  this  part  of  the  producer  to  fall. 

"Figures  11  and  12  represent  diverse  arrangements 
of  the  gratings  d,  designed  to  prevent  the  coal  from 
falling  out  laterally  into  the  passages  b  and  c,  for  the 
outlet  of  gas  and  inlet  of  air.  In  figure  11  the  grating  is 
formed  by  thin  bricks  h,  laid  flat  upon  bearers  i,  leaving 
passages  between  these  shallow  enough  to  prevent  the 
coal  from  sliding  outward.  In  iigure  12  the  grating  is 
formed  of  hollow  bricks  j,  arranged  in  quincunx,  or 
simply  superposed,  so  as  to  leave  numerous  passages  for 
the  gas  and  air,  while  they  prevent  the  coal  from 
obstructing  the  passages  b  and  c. 

"It  is  evident  that  the  forms  and  dispositions  of 
these  pieces  of  refractory  clay  may  be  greatly  varied 
without  inconvenience,  provided  they  are  arranged  to 
be  easily  withdrawn  and  replaced  through  the  openings 
e,  when  they  become  injured  from  use. 

"  Figures  13  and  14  represent  a  producer  in  which 
only  the  orifice  b  for  the  outlet  of  gas  is  closed  by  a 
grating,  d,  disposed  in  steps.  The  other  side  where  the 
air  i>  admitted  is  inclined,  and  if  a  similar  inclination  is 
given  to  the  grating,  the  layer  of  coal  traversed  by  the 
air  is  about  equal  at  all  points. 

"Figures  15  and  10  represent  a  producer,  in  which 
the  hot  air  enters  the  fuel  from  above,  and  the  gas  may 
go  out  through  one  side  or  both  sides  of  the  apparatus. 
The  drawing  represents  two  outlets,  b,  and  I  have  also 
increased  the  width  of  this  part  of  the  chamber,  so 
that    the    layer   of    fuel    traversed   by   the    air  may  be 


298  COMBUSTION   OF    COAL. 

as  uniform  as  possible.  It  will  also  be  observed  that  I 
have  provided  in  the  masonry  offsets,  k,  into  which 
the  fuel  may  slide,  and  which  will  tend  to  prevent 
the  hot  air  entering  by  the  passage  c  from  follow- 
ing the  inclosure  of  space  a,  and  compel  it  to  traverse 
the  fuel  before  reaching  the  outlets  b  for  the  gas. 

"The  air  which  supports  combustion  in  the  gas-pro- 
ducer acquires  the  force  necessary  to  enter  the  producer 
from  the  heat  which  it  receives  in  passing  through  the 
recuperator;  but  it  may  also  be  injected  either  by  means 
of  a  blower,  or  by  a  jet  of  steam,  or  by  a  blast-engine  of 
any  kind.  Of  these  methods  I  prefer  to  employ  the  jet 
of  steam,  because  the  steam  in  passing  through  the  fuel 
is  decomposed,  and  produces  a  gas  rich  in  carbon.  I 
obtain  this  result,  when  the  aif  is  not  forced,  by  admit- 
ting into  the  lower  part  of  the  recuperator  a  small 
quantity  of  water  by  means  of  an  iron  tube  which  is 
inserted  into  the  air-inlet,  as  shown  in  figure  1.  This 
water  is  vaporized  in  the  iron  tube,  and  escapes  as 
steam  into  the  recuperator. 

"I  am  aware  that  a  gas-producer  has  been  described, 
in  the  operation  of  which  previously-heated  air  was 
introduced  to  support  the  combustion  of  the  gas-pro- 
ducing fuel.  Two  regenerators  and  conduits  alternately 
carried  a  current  of  air  to,  and  a  current  of  gas  from, 
the  producer,  and  these  currents  were  reversed  for  the 
purpose  of  heating  the  air,  but  with  the  effect  of  cool- 
ing the  gas.  Each  conduit  and  regenerator,  therefore, 
was  alternately  filled  with  gas  or  with  air,  so  that  with 
each  reversal  of  the  currents,  the  gas  contained  in  the 


A.PONSARD. 
PROCESS  6  APPARATUS    FOR  GENERATING  GASEOUS    FUEL. 


V 


/7S.4. 


r 


poxsard's  process  axd  apparatus.  299 

one  was  returned  through  the  fuel,  while  the  air  con- 
tained in  the  other  was  delivered  into  the  flue  leading 
to  the  furnace,  where  it  would  mix  with  and  deteriorate 
the  quality  of  the  gas.  In  this  case  the  length  of  the 
flue  to  the  furnace  permitted  an  admixture;  hut  with  a 
delivery  directly  into  the  furnace,  such  as  I  contem- 
plate and  set  forth,  the  flame  would  he  extinguished, 
and  its  place  supplied  by  a  blast  of  heated  air  alone  at 
each  alternation,  which  would  not  only  diminish  the 
heat,  but  oxidize  the  contents  of  the  furnace." 


INDEX. 


PAGE 

Acid,  sulphurous  in  smoke 162 

Air 25 

Air,  admission  of  above  the  fuel 113,  14i! 

Air,  :: 

Air,  admission  of  told  above  the  fire 161 

Air,  composition  of 26 

Air.  distribution  of  in  the  furnace 141 

Air,  diathermacy  <>f 34 

Air,  difficulty  in  heating  or  cooling 134 

Air,  effect  of  heated 130 

Air.  heated  for  draft 215 

Air,  physical  properties  of 30 

Air,  quantity  affecting  temperature 121 

Air,  required  for  combustion 126,  132 

Air,  temperature  at  high  altitudes 32 

Air,  transparency  of 34 

Air,  weight  of 30 

Albertite,  in  gas  making 63 

Alcohol,  flame  of 11.", 

Alumina,  in  ashes 169 

Ammonia 33,    91 

Analysis  of  coal 81 

Anthracite  coal 78 

Anthracite,  action  in  the  tire 79 

Anthracite,  rate  of  combustion n;> 

Apparatus  for  gas  analysis iti 

Area  of  chimneys 136 

si 

Ashes,  analysis  of 169 

Ashes  and  clinkers 168 

Ashes,  color  of 170 

Atmosphere 25 

Aim  isphere  of  the  coal  period in 

Atmosphere,  physical  properties  of 30 

phere,  weight  of 31 

Atoms :; 

Atomic  weights 7 

Atomic  weights  and  specific  heal 196 

ind  mob  cules "> 

Benevines,  on  flame llfi 

Berthler,  on  heated  air 130 


PAGE 

Bitumen,  not  in  coal 53 

Bituminous  coal 52 

Bituminous  coal,  analysis  of 55,    00 

proj 

Bituminous  coal,  rate  of  combustion 119 

Bituminous  coal,  Illinois 55 

Bituminous  coal,  Indiana 56 

Bituminous  coal,  Kentucky 59 

Bituminous  coal,  Ohio 60 

Bituminous  coal,  Pennsylvania 57 

Blandy,  V.  Z.,  analysis  by 55,    56 

ianon  flame 115,  116 

Block  coal 64 

Boetius'  furnace 129,  134 

Boiler  and  chimney  connections 140 

Boiler  corrosion 163 

Boulton  and  "Watt  on  chimney  heights..  140 

Boyle's  law 30 

Bridge-wall,  McMurray's 153 

Brown  coal  and  lignite 42 

Bunsen  burner,  flame  in 114 

Burning  smoke 160 

Caking  coals 61 

1  alorie 206 

Calorific  power  "f  coal 182,  184 

t  laloi  Lfic  power  of  Strong's  gas 274 

Calorimeter,  Favreand  .^ilbermau 179 

Calorimeter,  Thompson's 188 

Candle  power  explained 62 

<  'an in 'l  COal 73 

Cannel  coal,  analysis  of 74,    76 

Cannel  coal,  ill  gas  making 63 

Cannel  coal,  In. liana 7"i 

Cannel  coal,  Kentucky 74 

Cannel  coal,  Pennsylvania 71 

Capacity  fur  heat 199 

Carbon 87 

Carbon  and  oxygen v^ 

1  Sorbon,  air  required  fur 182 

Carbon,  how  it  spontaneously  Ignites....  229 
Carbon,  molecular  weight  of 6 


302 


INDEX. 


PAGE 

Carbon,  specific  heat  of 88 

Carbon,  temperature  of  combustion  of...  121 

Carbon,  units  of  heat  in 182 

Carbonic  acid 158 

Carbonic  acid  in  atmosphere 33 

Carbonic  acid  in  plants 20,    22 

Carbonic  oxide 158 

Carbonic  oxide,  effect  of  on  health 282 

Carbonization  of  coal 05 

Carbureted  hydrogen 90 

Charcoal  37,     38 

Chemical  action 100 

Chemical  affinity 108 

Chemical  analysis 81 

Chemical  and  mechanical  changes 3 

Chemical  and  physical  changes 2 

Chemical  properties  of  bodies 2 

Chemical  separation,  energy  of I04 

Chevandier,  M.  Eugene,  quoted 37 

Chimneys 210,  217 

Chimneys,  draft  in 136 

Chimneys,  height  of .137,  13!),  140 

Clinkers 168 

Coal,  analysis  of 81 

Coal,  anthracite 78 

Coal,  bituminous 52 

Coal,  brown 42 

Coal,  caking 61 

Coal,  cannel 73 

Coal,  carbonization  of 65 

Coal,  classification  of 35,    52 

Coal,  combustion  of 106 

Coal,  conditions  necessary  to  burning 108 

Coal-dust  fuel 233 

Coal,  elementary  analysis 84 

Coal,  elements  found  in 7 

Coal,  evaporative  power  of 191 

Coal,  experimental  calorific  power  of 186 

Coal,  formation,  area  of  in  the  U.  S 15 

Coal,  fusion  of 1 

Coal,  free  burning Go 

Coal,  for  gas 61 

Coal  gas,  composition  of 91 

Coal,  Indiana  block 64 

Coal,  molecules  of 2 

Coal,  non-coking 61,     G4 

Coal,  parrot  74 

Coal,  phosphorous  in 85 

Coal,  physical  properties  of 1 

Coal,  products  obtained  from 94 

Coal,  proximate  analysis 83 

Coal,  proximate  constitution  of 184 

Coal,  quantity  of  gas  in „ 26 


PA'i  E 

Coal,  rate  of  combustion 118,  119 

Coal,  required  for  good  coke 70 

Coal,  semi-anthracite  77 

Coal,  semi-bituminons 76 

Coal,  spontaneous  ignition  of 226 

Coal,  sulphur  in 85 

Coal,  theoretical  calorific  power 182 

Coal,  vegetable  origin  of 16,     21 

Coke 65 

Coke,  Connellsville 65 

Coke,  experiments  on 66,    70 

Coke,  from  lignites 43 

Coke,  kind  of  coal  required  for  a  good....     70 

Coke,  manufacture  of  in  England 71 

Coke,  quality  affected  by  temperature...     66 
Coke,  quantity  produced  in  gas  works...    63 

Coking,  heat  developed  in 7" 

Coking,  loss  in 72 

Color  of  ashes 170 

Color  of  leaves  due  to  sunlight 21 

Combustion 98 

Combustion,  air  required  for 127 

Combustion,  available  heat  of 123 

Combustion,  and  hot  air 128,  130 

Combustion,  and  ignition lio 

Combustion,  and  light 110 

Combustion,  conditions  necessary  to 109 

Combustion,  in  reverberatory  furnaces..  131 

Combustion,  nature  of 105,  107 

Combustion,  of  coal  and  coke 215 

Combustion,  products  of 159 

Combustion,  rate  of 117 

Combustion,  table  of  heat  units 180 

Combustion,  table  of  temperatures 123 

Combustion,  theory  of 107 

Connellsville  coke 65 

Cornut,  M 166 

Corrosion  of  boilers 1(3,  166 

Cost  of  making  water  gas 277 

Cox,  E.  T.,  analysis,  methodsof 82 

Cox,  E.  T.,  analysis,  bituminous  coal,  55,  59 

Cox,  E.  T.,  analysis,  cannel  coal 75 

Cox,  E.  T.,  analysis,  lignites  44,    50 

Cox,  E.  T.,  experiments  in  coking 67 

Cramptoii'sexper'ts  with  powdered  fuel,  233 

Davy,  Sir  H.,  on  flame Ill 

Definite  proportions 101 

Deflectors  in  locomotives 12!i 

Degraded  energy 24 

Diffusion  in  gassesand  liquids ". 

Doors  for  furnaces 162 

Doville,  M 16:; 

Draft,  artificial 21:: 


INDEX. 


303 


PAGE 

I>r;ift  for  different  fuels 141 

Draft  in  i  himneys 136 

Dynamical  theory  of  heat 195,  'Jul 

Elementary  analysis  of  coal 84 

-V     11 

Energy,  dissipation  of .' 22 

Energy  of  chemical  separation 104 

1 15  j 

Energy,  not  reversible 2:! 

Energy,  transmutation  of 13 

Energy,  types  of ll 

English  coals,  rate  oi  combustion 1  is 

Equivalent  evaporation 192 

Equivalents,  law  of 102 

Equivalent  numbers 5,  l"". 

Evaporation,  latent  beat  of 202 

Evaporation  per  pound  of  fuel. ..157,  191,  193 
Explosion Ill 

Fan  blast W2 

Favre  and  Silberman 178 

Fire,  temperature  of 120 

Firing 161,  211,  218 

Flame  : Ill 

Flame  and  cold  bodies 117 

of 113 

of  hydrogen 11-1 

Flame,  luminous 1 1 4 

Flame,  temperature  ol  gas 274 

Flame  under  pressure 115 

Fool  pound 1 1 

Frankland  "ti  flame 115 

Free  burning  coal 65 

Fuel "••"> 

Fuel,  energy  of 15 

Fuel,  mixture  for  calorimeters 190 

Fuel,  products  of  carbonization 36 

Fuel,  specific  heal  of 200 

Fuel,  thermal  power  of its 

Fuel,  w  i  teof 284 

Furnace  defined 123 

Kuni  I  11  :,   !  : 

Furnace  draft  136 

Kuni  ,   of 128 

Furnace,  losses  in 124 

Furnace,  requisites  "t" 209 

Fusion,  latent  heat  of 202 

*  laa,  advantages  of  as  a  fuel 257 

nalysis 172 

il  ill 

ike <•<'< 

<ia>  from  water 260 

trnaces,  hot  air  in 129 


PAG  K 

Gas  from  a  ton  of  coal 62 

Gas,  standard  of  Illumination 62 

<ias,  sulphur  in 92 

(ias.  Strong's;  a  report  on 271 

Gaseous  fuel 254 

G   -  -   cooling  of 212 

Gases,  specific  heat  of 197 

table  of  heated 138 

G   -  s,  temperature  of  escaping 141 

Gasi  s,  volatilization  of,  from  coal 212 

■■•  eight  of,  escaping 139 

(..  isenheimer's  hot  blast 129 

Gorman,  W.,  gas  furnace 130 

Grahamite,  in  gas  making 63 

Grate-,  length  of 161 

t  i-rates  recommended 172 

Grates,  size  of 14o 

Grothe's  cupola I2w 

Gruuer,  Professor,  quoted 267 

<  in  ti  powder 99 

Hanet-Clery,  M 162 

Hartford  Steam  Boiler  Ins.  Co 156 

Heat 195 

Heat,  absorption  of  by  forests 20 

action  of  on  clinkers 171 

Heat,  a  form  of  energy 23 

Heat,  devi  loped  by  chemical  action 178 

Heat,  developed  in  coking 73 

Heat,  generated  by  friction 14 

Heat,  generated  by  impact 14 

Heat,  how  available 124 

Heat,  latent  201 

Heat,  losl  in  furnaces 210 

Ileal,  of  combustibles,  table  of 180 

Heat,  of  combustion 107 

Heat,  required  in  a  puddling  furnai  e 285 

Heat,  required  to  melt  steel 

Heat,  theory  of 19.ri 

Heat,  transfer  of 23 

Heated  air  and  chemical  action 131 

Heated  air  for  combustion tjs 

Heumann's  experiments  on  flame 116 

Hoffman's  kiln  129 

Horse  power II 

Howatson's  furnace 130 

Hydrogen - 

Hydrogen,  as  a  unit •">,  103,  197 

Hydrogen  and  nitrogen 91 

Hydrogen,  atomic  and  molecular  w  -his 

Hydrogen,  burning  of 90 

Hydrogen,  flam  lof 114 

Hydrogen,  gas  from  water 91 

;en,  liquid h'-' 


304 


INDEX. 


PAGE 

Hydrogen,  quantity  of  in  water 90 

Hydrogen,  solid 89 

Ignition  and  combustion 110 

Irish  peat 40 

Ireland's  cupola 1-9 

Iron,  action  of  sulphur  on 167 

Iron  in  ashes 169 

Iron  pyrites 170 

Iron,  sesquioxide  of  170 

. ood  on  draft  area 137 

Johnson,  analysis  of  coal 74,  77,     80 

Joule,  I>r 204,  205 

Kane,  Sir  Robert,  quoted 40 

]  leg 

Kilogrammetre 11 

Kinetic  energy 11 

Knapp's  experiments  on  flame 115 

Krigar's  cupola 129 

Lamine,  M 167 

Latent  heat 201 

Latent  heat  of  evaporation 202 

Latent  heat  of  fusion  202 

Law  of  equivalents 102 

Law  of  gaseous  volumes 8 

Levette,  (j.  M.,  experiments  on  coke 67 

Light  and  combustion llo 

Light,  effect  of  on  plants 21 

Light  produced  by  combustion 107 

Lignite 35,    42 

Lignite,  Arkansas 48 

Lignite,  Colorado  47 

Lignite,  Foreign 51 

Lignite,  Kentucky 44,     49 

Lignite,  Texas 50 

Lignite,  Vancouver's  Island 46 

Lignite,  Washington  Territory 45 

Lignite  and  brown  coal 42 

Lignite  as  a  fuel 43 

Lignite,  calorific  power  of 1S7 

Lignite  coke 43 

Lignite,  water  in 44 

Liquefaction  of  hydrogen 89 

Liquid  fuel 245 

Lime,  incandescence  of 110 

Lime,  quantity  of  to  purify  gas 63 

Locomotives,  rate  of  combustion  in. .118,  120 
Luminous  flames 114 

McFarlane,  James,  quoted 61 

McMurray,  R.  K.,  bridge  wall 153 

Maniotte's  law 30 


PAGE 

Marsilly,  M.,  on  coking 67 

Martin's  furnace  door 148 —  151 

Mayer,  Dr 204 

Mechanical  flring 218 

Mechanical  intermixture  and  chemical 

combination 99 

Mechanical  theory  of  heat 195,  203,  204 

Meunier-DollfuB 165 

Multiple  proportions 101 

Muriate  of  zinc 9? 

Molecules t ;; 

Molecules  and  atoms 5 

Molecules,  motion  of ?. 

Molecules,  number  of  atoms  in 6 

Molecules,  weights  of 6 

Moore,  G.  E  -    ;as 27n 

Mott,  Henry  A.,  Jr.,  table  of  products 

obtained  from  coal 94 

Mount  Vernon,  N.  Y.,  gas  wks...203,  265,  270 

Neilson,  heated  air  in  furnaces 128 

Net  combustible 117 

Newport  puddling  furnace 130 

Nitrogen 158 

Nitrogen  and  hydrogen 91 

Nitrogen  and  oxygen 29 

Nitrogen,  molecular  weight  of 6 

Nitrogen,  properties  of 27 

Non-caking  coals 61,     64 

Norwood,  Dr.,  analysis  by 55 

Orsat,  M.  De  H 174 

Ougree  iron  works  162,  164 

Owen,  D.  D.,  analysis  by 74 

Oxygen 29 

Oxygen  to  be  deducted  from  fuel 181 

Oxygen,  molecular  weight  of 6 

Ozone 34 

Parrot  coal 74 

Peat 35 

Peat,  analysis  of 40 

Peat  charcoal 42 

Peat  formation 39 

Peat,  product  of  distillation 41 

Peat,  properties  of 39 

Peat,  use  of  in  locomotives 41 

Peat,  water  in 40 

Peclet,  on  heated  air 130 

Percy's  classification  of  fuel.... 35 

Perforated  pipes  in  furnaces 152 

Perpetual  motion 22 

Peter,  Prof.,  analysis  by 58,    75 

Petroleum 245 


INDEX. 


305 


PAGE 

Petroleum,  calorific  power  of 246 

Phosphorous  in  coal -  i 

Phosphorous,  molecular  weight  of 6 

Plants  of  the  coal  period 17 

Ponsaid  furnace 129 

Ponsard  furnace,  description  of 290 

Ponsard  recuperator 134 

Potential  energy 11,  104 

Powdered  fuel,  experiments 234 

Pressure  of  gases,  cause  of •' 

Pressure,  influence  of  in  coking 67 

re  of  air 4 

Prideaux,  T.  S 129 

Prideaux,  fut  aa  :e  door 143 

Prideaux,  on  combustion 132 

Products  obtained  from  coal 94 

Products  of  combustion II 

Proxii  is  81,     ■  "• 

Puddling  furnace 213 


Qualitath  e  analysis... 
Quantitative  analysis  . 


Bain,  cause  of 

Rankine,  on  heated  gasses 

Rate  of  combustion 

I*«<l  ash 

ill,  M  

ill.  M.,  analysis  of  Lignites 

Reverberatory  furnacefi 

Rogers,  B.  D.,  classification  of  coal.... 

; •  1 1 1 1 >  coal,  rate  of  combustion... 


81 
81 

30 
137 
117 
170 
196 

51 
131 

62 
118 

Samples  for  analysis 82 

Semi-anthracite  coal '" 

Bemi-bituminous  coal ",;.  77 

ixide  of  lion '  ■'' 

Bheurer,  Cestnerand  Meunier-Dollfus...  184 

Ships  and  spontaneous  combustion 223 

17 

Silica  in  ashes 169 

Beimens,  Dr.  William 211 

Seimens'  crucible  furnace 267 

■  '  furnaces 129 

278 

»'  gas  temperature  of  Dame 27s 

Seimi  n  '  gat  and  water-gas 



Seimens'  regeni  rative  gas  furnai  i 

Skeel,  I'll.  n. n 

Smith's  furnai  e  door 219 

Smoke ' 

Smoke,  burning 16 

Smoke,  pr<  mention 161 


PAG  E 

Smoke,  sulphurous  acid  in 162 

Soot 161 

Soot,  anal]  si-  of 165 

Soot,  in  flame 159 

Source  of  energy 16 

Specific  heat 199,  133 

Specific  heat  and  atomic  weights li'G 

Specific  heat  of  carbon 88 

Specific  In  at  of  gases 197,  201 

Spontaneous  combustion 223 

steam  jel  for  draft 136 

9S  of  beat  in  melting 285 

Stein  on  flame !!."> 

Structure  of  flame Ill 

Sunlight,  chi  mica]  efle<  ts  of 20 

Sun,  rays  of  a  source  of  motion 11' 

Sun,  the  source  of  energy 16 

Stevenson's  apparatus  for  burning  pow- 

i    ed  fuel 239 

Strong's  gas  as  a  fuel 276 

Strong's  gas,  composition  of 27  I 

•  osl  of 277 

Strong's  gas,  economic  value  of 275 

Strong's  ga  ,  for  illuminating 281 

For  metallurgy 2S1 

as  f  ir  generating 2(>1 

Sulphate  of  iron 166 

Sulphur 92,  158 

Sulphur  a  cause  of  corrosion  162 

Sulphur,  action  of  on  iron 1117 

Sulphur,  chemical  relations  of 92 

Sulphur  in  coal,  determining  the 85 

Sulphur  in  gas  coal 63 

•in  water-gas 273 

Sulphur,  molecular  weight  of  ,; 

Sulphurous  acid 149 

Sulphurous  acid  in  smoke 162,  166 

Sulphurous  oxide 158 

Symbols,  not  merely  abbreviations 9 

Symbols,  wh]  used. 8 

Lie  formulas,  how  made !l 

Symbolic  notation 8 

Temperature,  advantages  of  a  high 180 

ature,  at  which  light  is  emitti  d..  1 10 

Ti  mperature,  effect  of  a  uniform •_'! 

T\  mperature,  Influence  In  coking 66 

rature,  of  combustion,  table  of....  128 

T<  mpi  i    i'H",  of  fire 12'' 

Thermal  power  of  fuels 178 

todj  oamics,  first  law  of 208 

Thompson's  calorimeter 188 

Transmutation  of  energj  13 


306 


INDEX. 


PAGE 

Tyndall,  estimate  of  Mayer  and  Joul   . 

Tyndall,  theory  of  combustion 1  7 

Unit  of  heat 206 

Unit  of  work 11 

U.  S.  Govt,  experiments,  furnace  door..  151 
U.  S.  Govt. experiments,  pondered  fu 

Vapor  in  the  atmosphere 32 

Vincent,  Chas.  W.,  quoted 223 

Violette,  M.,  quoted 36,    38 

Volatile  matter  in  coal 52 

Waste  gases 216 

Waste  gases,  the  utilizing  of 284 

Water  and  spontaneous  combustion 230 

Water  gas 260 

Water-gas,  analysis  of 265 

Water-gas  and  Siemens' gas 265 

Water-gas,  objections  to 283 

Water-gas,  obtained  per  ton  of  coal 2G3 

Water,  quantity  of  hydrogen  in 90 

Water,  specific  heat  of 199 


PAGE 

Water,  temperature  of  max.  density 207 

Whepley  and  Storer 234 

White  ash 170 

Wibelon  flame  115 

Williams,  C.  Wye.,  furnace  door 14:5 

Wills,  Dr.  Thos.,  quoted 92 

Field  andAydon '-'is 

Wormley,  T.  G.,  analysis  by 60 

Wood 35 

Wood,  as  a  fuel 36 

Wood,  composition  of 37 

Wood,  conversion  into  coal 16,     22 

usure 16 

Wood,  gas 282 

Wood,  moisture  in 36 

Woody  fibre,  formation  of 20,    22 

Work  converted  into  heat 13 

Wurtz,  H.,  analysis  by 245 

Youghiogheny  coal 58,    62 

Zinc,  action  of  muriatic  acid  on 99 


TABLES 


PAGE 

I.     Molecular  weights 6 

II.    Elements  found  in  coal 7 

III.  Compounds  of  nitrogen  and  oxygen 29 

IV.  Water  expelled  from  wood  at  various  temperatures 36 

V.     Composition  of  wood 37 

VI.    Composition  of  charcoal 38 

VII.    Composition  of  peat 40 

VIII.     Products  of  the  distillation  of  peat 41 

IX.     Analysis  and  heating  power  of  lignites 61 

X.    Coals  coked  under  different  pressures 67 

XI.    Composition  of  carbonic  acid  and  oxide 88 

XII.     Products  obtained  from  coal 94 

XIII.  Specific  gravity,  atomic  weight  and  equivalent  numbers  of  elements  found 

in  coal 103 

XIV.  Rate  of  combustion,  anthracite  coal 119 

XV.    Temperature  of  combustion 123 

XV!.     Air  required  for  combustion  of  various  fuels 127 

XVII.     Volume  of  gases  at  ditT;rent  temperatures 138 

XVIII.     Experiments  with  the  Asheroft-Martin  furnace  door 151 

XIX.     Seal  'i  -veloped  by  complete  combustion 180 

XX.     Units  of  heat  in  carbon Ig2 

XXI.     Experimental  and  theoretical  calorific  power  of  coal 186 

xxil      Experimental  calorific  power  of  coal  and  lignite 1S7 

XXUf.    Specific  heat  of  simple  gases in: 

XX  IV.     I'roducts  of  specific  heal  into  atomic  weights 198 

XX  V.     Specific  heat  of  fuels 200 

XXIV.    Specific  hi  .  201 


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